Macintosh OS X Routine Maintenance
By Randy B. Singer

Copyright © Randy B. Singer, 2004 - 2006. All worldwide rights reserved.
Permission is hereby given to link to this site, but no other use is permitted without express written permission.

Covers OS X 10.2 through OS X 10.4
Note: Not all products mentioned, at the time of this writing, have been updated to be Intel-compatible.



I've created this site because so many of the Macintosh users that I have encountered have expressed frustration that they don't know what to do, or what to use, for performing routine maintenance on their Macintosh running OS X. There is also a huge amount of misinformation going around on the subject. Even Apple has contributed to the confusion with conflicting tech notes on their Web site. With the assistance of a few free utility programs, routine maintenance under OS X is very easy. The problem for most users is figuring out which utility to use, and for what. This site will tell you that.

Just a little routine maintenance can be as effective as buying an expensive accelerator for some Macintoshes! It can also banish vexing spinning beachballs, rid you of "out of memory" error messages, make an old Mac perform like a newer one, and keep your valuable data from being lost.

The philosophy behind this site:
This is not (necessarily) a site for experts and power-users. What I recommend here is what I see as the easiest, quickest, surest, least intimidating, and least expensive way to accomplish valuable routine maintenance. If you enjoy inputting arcane commands at a UNIX prompt, if you know UNIX inside and out, if you have money burning a hole in your pocket for commercial software with lots of questionable features, or if you enjoy playing around with the features of powerful (and potentially dangerous) software that you don't really understand, this site isn't meant for you. I freely admit that there are other ways to do the routine maintenance suggested on this site, but the procedures that I recommend here are designed to be the best ones for the average Macintosh user.

I've tried to make it easy as possible. I tell you what you should do, and what you should do it with, and roughly how often. If you are an average user, you can just follow my recommendations and be happy that you have done what is necessary. If you want to know more...the "why," or the other options, or any controversy that exists in the Macintosh community over the need for these procedures, I've provided a "Discussion" section for each bit of routine maintenance, as well as a bunch of linked citations.

There are several very common myths circulating about Macintosh maintenance. I don't know anywhere else where they are all acknowledged in one place. I mention them all on this site. Look for the headings: "Maintenance Myth."

Note: Many problems that one might experience while running OS X, especially performance and memory error problems, can be traced to not having enough RAM (memory) installed. The amount of RAM that comes standard with a new Macintosh (assuming that you haven't paid to have more RAM installed at the time of purchase) is the bare minimum necessary, and adding more RAM to your Mac is usually a good idea. In my personal opinion, in no case should a Mac running OS X have less than 512MB of RAM, for decent performance. More is just about always better. See:
http://homepage.mac.com/simx/mughelp/English/overview.html
If you want to find out if you need more RAM, try this free utility:
"Do I Need More Memory?"
http://www.hillmanminx.net/dinmm/index.html

This page doesn't cover troubleshooting hardware problems. For instance, many, maybe even most kernel panics
http://docs.info.apple.com/article.html?artnum=106227
under OS X, are caused by hardware problems such as bad RAM, defective USB hubs, incompatible PCI cards, etc. For more information on troubleshooting hardware, please have a look at my Jaguar and Panther troubleshooting Web sites, referenced below.

Disclaimer:
When using any disk utility, there is always the slim possibility that things can go horribly wrong. So, it is always a really good idea to have an up to date backup of all of your important data before using any disk utility. Actually, its just simply a good idea to always keep a backup of your data in any case, because hard drives are notorious for failing when you would least expect them to and you can least afford them to. For backup software, I suggest that you check out SuperDuper ($28)
http://www.shirt-pocket.com/SuperDuper/SuperDuperDescription.html
and consider getting a FireWire hard drive to backup to. I prefer Seagate hard drives:
http://www.seagate.com/products/retail/external/usbfirewire

If you are experiencing a problem with your Macintosh, performing all of the suggested routine maintenance on this page will often fix the problem. If it doesn't fix the problem, check out my two OS X troubleshooting Web sites:

How To Deal With Common OS X 10.2 Jaguar Problems
http://www.macattorney.com/tutorial.html

How To Deal With Common OS X 10.3 Panther Problems
http://www.macattorney.com/panther.html


This page only refers to Macintosh OS X versions 10.2, 10.3, and 10.4. If you have an earlier version of OS X I strongly advise upgrading to a more recent version, as OS X, in my personal opinion, didn't become a really good product until version 10.2.

The routine maintenance necessary for OS X 10.2, 10.3 and 10.4 is similar, but 10.4 can often handle corrupted user preferences files automatically, and you no longer have to run the built-in maintenance scripts manually under 10.4.3 and later.


Return to Table Of Contents

1) REPAIR DISK PERMISSIONS

Slow operation and generally unusual behavior are signs that may mean that permissions need to be repaired on your Macintosh's hard drive. To do so you can run Repair Disk Permissions from within Disk Utility, located on your hard drive at:
Applications/Utilities/Disk Utility
Note: There is no need to verify permissions before you repair them. Unless you can read the report and understand what Disk Utility proposes to do, there is little point in verifying first.

For some reason permissions often seem to get fouled up under OS X 10.2. Under OS X 10.3, and OS X 10.4, file permissions are less of a problem. But you should still run Repair Disk Permissions regularly. Maybe once a month, and every time after you have installed new software.

Open Disk Utility, and on the left side of the screen select your hard drive, then select the First Aid tab on the right side and click on "Repair Disk Permissions."

See http://docs.info.apple.com/article.html?artnum=106712 and
http://docs.info.apple.com/article.html?artnum=107298 for further details.

More information about how to repair permissions:
http://www.ncmug.org/tips/repair_permissons.html

Note: Some users are reporting that they run Repair Permissions over and over again, and the same permissions are reported as being wrong, and they are not being repaired. You should know that, in addition to reporting faulty permissions, until very recent versions of OS X, running Repair Permissions in Disk Utility also gave you advisory messages. For instance, it might report that it is using an updated set of rules to determine if any permissions needs to be repaired. These are not error reports and they will not change no matter how many times you run Repair Permissions. Advisory messages do not indicate that anything is wrong, and they can safely be ignored. Example:
"We are using special permissions for the file or directory
./System/Library/Filesystems/hfs.fs/hfs.util.
New permissions are 33261"
http://docs.info.apple.com/article.html?artnum=107298
As of OS X 10.4.6, Repair Permissions no longer gives these advisory messages.
http://docs.info.apple.com/article.html?artnum=303411

Discussion.

Maintenance Myth #1: "You need to repair permissions from a copy of Disk Utility that resides on the drive that you are repairing."
This is a myth that is very prevalent.

It used to be that you were warned against repairing permissions on one disk while booted from another because only the receipt files on the drive you were booted from would be consulted, not the receipt files on the drive you were repairing, and thus not all permissions would be set correctly. Though it hasn't been documented by Apple, this is no longer necessary. As of late in OS X 10.2, you can run Repair Permissions while booted from a disk other than the one that you are repairing (e.g. the OS X installer CD-ROM), and it will correctly use the receipts on the disk being repaired.

From Macintouch (http://www.macintouch.com) on 2/18/06:

Dan Frakes (author of the excellent book Mac OS X Power Tools and a regular columnist in Macworld magazine), followed up on "repair permission" confusion:

David Marshall wrote, "Those who warn against repairing permissions on one disk while booted from another seem to be basing that warning on a mistaken premise...In fact, repairing permissions uses the receipts from the /Library/Receipts folder on the volume you're repairing permissions on, not the volume you're repairing them from."
This likely stems from the fact that in older versions of Mac OS X (pre-Jaguar, I believe), the Repair Permissions procedure did indeed use the /Library/Receipts folder on the boot volume, even if you were trying to fix an alternate volume. (This was even noted in Apple's support documentation. For example, if a permissions issue prevented you from booting off your normal boot volume, Apple recommended using the Repair Permissions function while booted from the Mac OS X Install disc and then, once you were able to successfully boot from your normal volume, use the procedure again to ensure the "correct" receipts were used.)
In Jaguar (again, as I recall), the procedure was changed -- without much documentation -- to use /Library/Receipts on the volume being repaired, boot or not. Unfortunately, many people who had become familiar with the original procedure never realized it had changed.

See Mark Douma's Disk Utility post in the Apple Discussions User Tips Library for more info.
http://discussions.apple.com/thread.jspa?messageID=607431


Maintenance Myth #2: There are some folks who are very adamant that you *never* need to repair permissions under OS X. While repairing permissions isn't a panacea, they are wrong, it is definitely worth your while to repair permissions occasionally. The reality is that running Repair Permissions doesn't require that you purchase anything to do it, it can be accomplished fairly quickly, it doesn't hurt anything, and after repairing permissions sometimes the problem(s) that the user is experiencing are gone. In addition, sometimes the curative effects of repairing permissions are repeatable and predictable. I don't see any reason not to do it.

Apple offers a list of reasons why you may need to repair permissions
http://docs.info.apple.com/article.html?artnum=106712

You also may want to note that Mac Help (the built-in help system that is part of OS X) tells you that repairing permissions should be done routinely.

Here is an example of the "it's never ever necessary" school of thought:
Exercises in Futility Part 2: Repairing Permissions is Useless
http://www.unsanity.org/archives/000410.php

And here is a contrary view:
The Tiger Report: The Great Repair Disk Permissions Mystery
http://macnightowl.com/news/2005/05/week3.htm

From the folks at MacFixIt, who recommend routine repair of permissions:
Another follow-up to the Repair Permissions debate
http://www.macfixit.com/article.php?story=20060505112437423
(Paid subscription required to access.)

The MacFixIt article makes this excellent point: While Disk Utility's Repair Permissions feature only repairs permissions for Apple Software (and not any third party software), much of that Apple software is system software, and that system software is used (and used often) by third-party applications. Thus, incorrectly set permissions can indeed cause problems with third-party applications.

These MacFixIt articles further explain what repairing permissions does, and they document real-world cases where repairing permissions was extremely helpful to users (Paid subscription required to access.):

Unravelling the Repair Disk Permissions controversy
http://www.macfixit.com/article.php?story=2006050407462364

Repair Permissions Success Stories
http://www.macfixit.com/article.php?story=20060728075547277

More Repair Permissions Success Stories
http://www.macfixit.com/article.php?story=20060731081527212

Dan Frakes has written an excellent article for Macworld on permissions and the need to repair them:
Repairing permissions: What you need to know
http://www.macworld.com/2006/08/secrets/repairpermissions/index.php


Return to Table Of Contents


2) RUN ROUTINE MAINTENANCE SCRIPTS
OS X runs its own (very basic) built-in maintenance routines, sometimes called "cron jobs," or "maintenance scripts," automatically between 3:00am and 5:30am each day. (There are daily, weekly, and monthly scripts.)
http://docs.info.apple.com/article.html?artnum=107388
You can find a rundown of what the built-in maintenance routines do at the bottom of:

http://episteme.arstechnica.com/6/ubb.x?a=tpc&s=50009562&f=8300945231&m=4630923435

However, prior to OS X 10.4.3, if you didn't leave your computer on 24 hours a day, or if you left it on but let it go into sleep mode, these routines weren't run. You can run these routines manually, whenever you want, with a free utility such as MacJanitor:
http://personalpages.tds.net/~brian_hill/macjanitor.html
If you are running OS X 10.3 or 10.2, you should probably run all of the cron jobs every few weeks. You can do this manually, or automatically on a schedule with one of the utilities mentioned below.

Maintenance Myth #3: You may have heard otherwise, but you don't need to use *any* utility, or perform any procedure, to make sure OS X's built-in maintenance tasks have run under OS X 10.4.3 and later.
http://arstechnica.com/reviews/os/macosx-10.4.ars/5
http://developer.apple.com/macosx/launchd.html
Tiger will run its cron jobs automatically (actually, they are no longer handled by the UNIX facility "cron," they are now handled by "launchd," if that means anything to you) whether you have left your computer on all night or not now. You no longer need a utility to run missed maintenance as of OS X 10.4.3. Actually, this was the case as of OS X 10.4.0, but a bug kept the maintenance routines from running more than once per restart. This was fixed as of OS X 10.4.3. Under OS X 10.4.3, missed scheduled routine maintenance scripts are automatically run at the next opportunity.

Update: Apparently Maintenance Myth #3, isn't yet a myth. According to this thread:
http://forums.macosxhints.com/archive/index.php/t-39005.html
and feedback that I have received, the mechanism for having OS X 10.4's built-in maintenance routines run automatically whenever necessary (that is, launchd) still hasn't been debugged successfully by Apple. So, it is still necessary when running OS X 10.4 to either routinely run the maintenance routines manually, or to use Anacron to make sure that they run automatically. (See below.)

Discussion.

If you want to be sure that the built-in maintenance tasks have been run, the daily, weekly, and monthly maintenance scripts each write the details of every run into their own log file, which you can check. Open the Console application (located at: Applications/Utilities/Console), go to File->Open Quickly->/var/logs/. Select "daily.out", "weekly.out", or "monthly.out" for the maintenance logs.

Anacron is a utility that will automatically run the built-in maintenance scripts at a time of your choosing. Install it and forget it. Nothing ever has to be manually launched to take care of all the maintenance scripts. Anacron does that job as well as the popular utility Macaroni, but it's free.

Anacron
3.1 for Tiger (OS X 10.4):
http://members.cox.net/18james/anacron-tiger.html

Anacron for those who haven't moved to Tiger yet:
http://www.alastairs-place.net/anacron.html


Return to Table Of Contents

Even though running the routine maintenance scripts clears out some temporary files, none of the system caches are touched by them. So it is a good idea to occasionally also use a utility that trashes the system caches, and occasionally your Internet browser caches. Deleting caches won't hurt anything. However, over time a cache speeds up your computer (assuming that you do some things repetitively), so if you aren't experiencing any problems, you may want to leave your caches alone. On the other hand, if it has been ages since you have flushed your caches, or if your computer is running slowly, or if you are experiencing odd problems, it might be a good idea to flush them. Use your discretion.

Cache Out X is a free program which cleans out system and internet browser caches. This can prevent some very hard to diagnose flaky behavior. (You may not want to regularly clear your browser cache if you have a slow speed connection to the Internet.) You can get Cache Out X from:
http://www.nonamescriptware.com/forums/index.php?act=Downloads
(Free registration required to access download area.)

According to MacAddict, October 2005, page 20, it is a good idea to occasionally clear out application-specific caches. They specifically recommend to clear out the two main cache folders in Mac OS X: 1) /Library/Caches, and 2)~/Library/Caches. ("~" stands for the folder with your username on it in your Users folder.) While Apple doesn't recommend doing this routinely, they indicate that it is a good idea in certain situations:
http://docs.info.apple.com/article.html?artnum=25398


A MacOSXHints tip also suggests clearing out the application cache files occasionally:
http://www.macosxhints.com/article.php?story=20060111202501460
This hint notes that there may be quite a few extraneous cache files in your ~/Library/Caches folder.

You get to the ~/Library/Caches folder by following the path:
[hard drive] --> Users --> [your user name] --> Library --> Caches.

You get to the /Library/Caches folder by following this path:
[hard drive] --> Library --> Caches

You should be able to delete everything safely. However, if you want to be extra careful, just create a new folder on your desktop, and drag everything from your Caches folder into it and restart. You can trash the folder on your desktop when you are certain that everything is running fine.

Tiger Cache Cleaner is a $9 utility designed to provide easy access to numerous OS X maintenance and utility options under OS X 10.4. Tiger Cache Cleaner can improve system performance by tuning internet and file caching settings and by implementing ram disks. Tiger Cache Cleaner can improve startup performance by eliminating duplicate or orphaned Login Items. Tiger Cache Cleaner can improve system performance by cleaning and rebuilding Spotlight metadata as well as providing powerful control options over Spotlight. Tiger Cache Cleaner Documents and the Tiger Cache Cleaner Engine can help maintain system health by providing set and forget automation of common maintenance chores. Tiger Cache Cleaner has the most comprehensive cache cleaning of any utility in its class.
http://www.northernsoftworks.com/tigercachecleaner.html


Return to Table Of Contents

3) CLEAR CACHES
4) REPAIR AND BACK UP PREFERENCES
Preferences become corrupted way too often under OS X 10.2. This is still a problem under OS X 10.3, but much less of a problem under OS X 10.4. If an application or applications quit unexpectedly under OS X, the first thing to suspect is that you have one or more corrupted user preferences files.

Preferential Treatment
http://homepage.mac.com/jonn8/as/
is a free utility that will check for corrupted preferences files. (It will sometimes even locate preferences files that are corrupted before you start experiencing any problems from them, so it is a good idea to use Preferential Treatment regularly. About once a week.) Preferential Treatment allows you to delete any corrupted preferences files from right within the program, so that they will be rebuilt on restart.

Once all of your preferences files are known to be in good shape, it is a good idea to back them up.That way, in the future if you have a problem with a corrupted preferences file, you can replace the entire corrupted file instantly with a clean copy. This also allows you to avoid having to re-set any application or system preferences.

A good utility to back up preferences files with, which will also allow you to quickly replace them with the backup if there are problems, is
'Back up user prefs', which is free.
http://www.m-t-software.com/software-backup.html
In the event of corruption of either individual preferences, or the entire folder, you can simply substitute the backed-up folder for the existing one using the program. This eliminates the need to troubleshoot your user preferences if you suspect that one of your preferences files is corrupted.

If an application unexpectedly quits under OS X 10.4 (Tiger), you are given the option of restarting that application with its ".plist" (preferences) file(s) deactivated, to see if that was the problem, and if it was, a new ".plist" is substituted for the old one. This approach isn't as pro-active as using Preferential Treatment routinely, but it should be entirely adequate and effective.

More information:
Tiger's new and improved “application crash” dialogs
http://www.macfixit.com/article.php?story=200505120750592
(Paid subscription required to access.)

Preferences Files: The Complete Story (Part V); How .plist files become corrupt and troubleshooting the results
http://www.macfixit.com/article.php?story=20060606082246983


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5) DO A FILE SYSTEM CHECK AND REPAIR DISK
I recommend that you occasionally restart your Mac, and hold down the Shift key right after the startup chime is played, and keep it held down until the spinning black bar cursor appears.

This procedure invokes what Apple calls a "Safe Boot":
http://docs.info.apple.com/article.html?artnum=106214
and your Mac will report that it has been booted (started up) into Safe Boot mode. During startup in Safe Boot mode your Mac will do a file system check, entirely in the background, with no working status indicated, or report generated, and any problems will automatically be repaired. It may take a while for your Mac to start up in Safe Boot mode. Once it has fully started up, you should immediately restart your Mac normally, because certain files are deactivated when you startup in Safe Boot mode.

Note: To startup (boot) into Safe Boot mode you must have a wired keyboard and mouse. A Bluetooth keyboard and mouse won't allow you to startup in Safe Boot mode.

Instead you may prefer to check your hard drive, and repair any problems, by using the method outlined below. The advantage of using the method outlined below is that both a working status indicator, and a report, are generated. The disadvantage is that you will have to have, and start up from, your OS X Installer CD-ROM.

Put your OS X Installer CD-ROM into your CD drive (if you have multiple installer disks, use the first one), and startup from it (by holding down the "C" key during startup or restart). From there you can choose Disk Utility from the Installer menu. Click on the disk that you want to repair in the left column and then the First Aid tab, and then click on Repair Disk. (If the Repair Disk button is gray, you either didn't click on the right thing in the left column, or you aren't started up from the Installer CD-ROM. You can't repair the disk that you have started up from.)

Discussion.

Longtime Macintosh users know that under OS 8 and OS 9, if you were experiencing nasty problems with your hard drive, that running Apple's Disk First Aid usually didn't fix them. In such cases, users often resorted to using the commercial product Disk Warrior, which could perform near miraculous feats of repair on your hard drive. It was also an invaluable tool for routine preventative maintenance. Under OS X, Disk Utility/Repair Disk is the replacement for Disk First Aid. So, the question most folks have is, 'is Disk Utility/Repair Disk as lame as Disk First Aid, and is Disk Warrior still an invaluable utility to have?' There is an interesting thread on TidBits Talk that covers this topic:
Looking for Disk Warrior Justification
http://db.tidbits.com/getbits.acgi?tlkthrd=2970

The answer is that Disk Warrior is a marvelous tool...when you need it. Fortunately, under OS X you don't need it as often as you needed it under previous versions of the Mac OS. For instance, you don't need to run Disk Warrior routinely as a preventative measure. (Though doing so, if you already own Disk Warrior, isn't a bad idea.) OS X is plenty stable without having to constantly rebuild its directory. And so, in my opinion, there is no need to purchase Disk Warrior unless a situation pops up where Disk Utility/Repair Disk reports that it can't repair a problem with your hard drive.. This is not to demean Disk Warrior. When you do need Disk Warrior, because your disk directory has developed errors that Disk Utility can't fix, it is a godsend to have.
http://www.alsoft.com/DiskWarrior/index.html

For further information about Disk Repair software, have a look at:
http://db.tidbits.com/getbits.acgi?tbart=07451,
with a follow-up on TechTool Pro at:
http://db.tidbits.com/getbits.acgi?tbart=07696

There are other ways to run a file system check/Repair Disk under OS X, such as by booting into Single User Mode, or by running the command "fsck" from the Terminal, but these are more advanced ways to do exactly the same thing, that I don't think that the average user needs to know about.
For more information than you need, see:
http://docs.info.apple.com/article.html?artnum=106214


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6) DEFRAGMENT A HARD DRIVE THAT IS LOW ON FREE CONTIGUOUS SPACE
Maintenance Myth #4: Most folks with an opinion will probably tell you that Mac's running OS X never need to have their hard drives defragmented.

Here is a quote from a MicroMat technician, that I think is very insightful:
The claim that installations of Mac OS X on HFS+ volumes do not fragment is a myth believed by people who do not have disk optimizers that allow them to see how much fragmentation their disks have. It is an example of ignorance that is not able to be removed by any amount of evidence. I think theologians call that “invincible ignorance.” It is now a widespread form of the pollution of information space.
http://tinyurl.com/yuqn4

Actually, some Macs running OS X can benefit quite a bit from defragmenting their hard drive. But not for the reason that you might expect. There is often little in the way of performance to be gained by defragmenting your hard drive. But defragmenting your drive can stave off some very flaky behavior, out of memory errors, and possibly even data loss.

OS X handles *file* fragmentation (a file being broken up into chunks and strewn across your hard disk) automatically, and fairly well, every time that you launch a fragmented file under 20MB.
http://article.gmane.org/gmane.comp.macosx.general/22906
http://arstechnica.infopop.net/OpenTopic/page?a=tpc&s=50009562&f=8300945231&m=9900929295
http://archives:archives@lists.apple.com/mhonarc/darwin-development/msg19702.html
http://macslash.org/article.pl?sid=03/10/29/190237
But it doesn't handle *drive* fragmentation (small bits of free space between files) well at all. In fact, OS X is prone to huge amounts of drive fragmentation.

Drive (as opposed to file) fragmentation under OS X is mostly irrelevant with respect to performance, as long as it isn't severe. Where hard drive fragmentation becomes important is when there are no longer any large contiguous chunks of free space left on your drive for OS X to use for working space, for virtual memory, temp files, databases, etc. When this happens, OS X can start acting flaky, and eventually, in extreme cases, it will suffer from data loss.

I used to recommend that folks defragment their hard drive when it was approaching 80% full (no matter how large the drive is), because I've heard from so many folks who were experiencing out of memory errors and flaky behavior at this level (no matter how large their drive was), and defragmenting invariably fixes the problem. But I've since heard from a number of users who made heavy use of their drive and they have experienced the problem as early as around 60% full. And other folks don't experience the problem until their drive is well over 80% full. Clearly how you use your drive makes a difference as to when, or if, you run out of free contiguous space on your hard drive.

So, now, instead of using a rough rule of thumb on when you should consider defragmenting your hard drive, what I recommend now is that folks check to see how much free contiguous space there is on their drive routinely, once their drive is over 50% full. You can do this quickly and easily with the free demo of iDefrag:
http://www.coriolis-systems.com/iDefrag.php
Or the free utility ShowVolumeFragmentation
http://people.freenet.de/amichalak/page1/page1.html
There is no need to purchase anything until and unless you need to. When you have no large chunks of free contiguous space left, you can expect problems to begin to appear if you don't defragment your drive. Note that if you let this problem advance too far, it may become impossible for any utility to work on your drive, protesting that there isn't enough free space on your drive for it to be able to run. (This despite the fact that you may have many gigabytes of "total" free space left on your drive.)

You may never need to defragment your drive (prior to purchasing a new one because the old one is becoming too full) or you may need to do so much earlier than you would expect, but by checking with one of these free tools you won't have to guess whether it is necessary or not.

If your drive needs to be defragmented, the *only* hard drive defragmentation utility that I recommend is iDefrag. (See my notes about other hard drive defragmentation utilities in Note 1, below.) It is the only one that I know of that can optimize the files on your hard drive in a totally OS X-savvy way. OS X, under OS 10.4, has a journal, a hot band, virtual memory, metadata, etc. to keep track of. It is very important that these things be located properly on the disk or performance will be compromised.
Technical data about the hot band and meta data on hard drives running OS X 10.4:
http://developer.apple.com/technotes/tn/tn1150.html#HotFile
iDefrag is the only hard drive optimization tool that does this perfectly (despite what some of the other companies that make hard drive defragmentation tools say.) Note: iDefrag does not, as of this writing, yet support Intel-based Macs.

The downside to iDefrag is that you can't do a comprehensive defrag without booting from a volume other than the one that you are defragmenting. Not everyone has a second hard drive. Coriolis Systems offers free software to allow you to make a boot CD-ROM to run iDefrag from, but using iDefrag this way isn't as safe as using it while booted from another hard drive.

Of course, another option, instead of defragmenting your hard drive, is to simply purchase a new, bigger, hard drive; copy all of the data on the old drive to the new drive, and then reinitialize (i.e. wipe clean) the old drive and start over with it. Moving all of your data from one drive to another will automatically defragment your data. Though it won't optimize it.

You have to reinitialize your data on the old drive for this plan to work, because if you just move *some* data from your old drive to your new drive, the old drive will still be badly fragmented, and without defragmenting the old drive it will still probably be flaky. (That is, even if you free up some space on the old drive, there more than likely still won't be the large chunk of contiguous free space available that the OS likes to have to run properly.)

Defragmenting your hard drive holds off any funny behavior from your OS because it frees up contiguous space, combining fragments of space into larger chunks of space.

Note that clearing off data from your drive, even a large amount of data, without also defragmenting, may not create enough *contiguous* space to keep your Mac running well.

Discussion.

Definition of Terms:
Types of Fragmentation:
1)"File" fragmentation, where files are broken up and are not contiguous
2)"Drive" fragmentation, where, though files may be contiguous, the free space on the drive is fragmented.

"Defragmentation" means that things (that is, data, e.g. files and applications, and free space) are made contiguous (that is, not broken up into small bits and strewn about at different places) on your hard drive.

"Optimization" means that not only is the drive defragmented, but data is put where it should be and/or it is put where it will provide optimum performance.

Let's refer to files A, B, C and D, and free space "__".

Here is a drive with no file fragmentation. All of the files are contiguous, but free space is fragmented. In other words there is no file fragmentation but there is disk fragmentation:
AAAAA__BBB__CCCCC__DDD_

Here is a drive with both the files and free space fragmented:
AA__BBA__CCCCCB__DDDAA_

Here is a drive with no file or free space (disk) fragmentation. All of the files are contiguous, and all of the free space is contiguous:
AAAAABBBCCCCCDDD______________

Now, take a look at that first example, where there is a lot of disk fragmentation even though all of the files are contiguous. Have you ever run a Mac under OS X with too little RAM? It was a dog, wasn't it? That's because your Mac was hitting your disk in a big way, using virtual memory instead of RAM for tasks. Now, think of the effect that you might see if you forced your Mac to use hundreds of little spaces all over your drive to write virtual memory to, instead of having it written to one big contiguous space. That's why drive fragmentation is more important than file fragmentation. OS X automatically defragments files. OS X doesn't do any drive defragmentation at all.

Note that if you actually defragment your hard drive as part of a routine maintenance program (rather than just keep track of how much free contiguous space is available), lets say every couple of months, then it won't take long to defragment your drive each time, and any potential problem will never rear its head. In addition you should be able to use close to every last gigabyte of space on your hard drive, and you will always have every last ounce of performance that your Mac can give you as a side benefit.

See Note #1, below, for more information on file defragmentation.


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7) CHECK S.M.A.R.T. STATUS
Hard drives are quite a bit more reliable these days than they were just a few years ago. Unfortunately, the old saying that "all hard drives die eventually" is still true. It would be nice to know in advance when a hard drive is going to fail. That way you would have time to backup your data before your drive ultimately met its end. S.M.A.R.T. (Self-Monitoring Analysis and Reporting Technology) is a feature built into most modern hard-drives that acts as an "early warning system" for pending drive problems. OS X 10.3 and above have this ability built-in, but it only works if the actual hard drive in your Mac has this technology built-in also. Disk Utility, which comes with OS X (it is in your Application/Utilities folder), under OS X 10.3 and above can tell you the S.M.A.R.T.-status of your hard-drive. Unfortunately, you have to remember to regularly launch Disk Utility to check this. (See below for free utilities that will automate this process.)

To check your drive's S.M.A.R.T.-status using Disk Utility, launch Disk Utility and select your hard drive. If at the bottom of the window it says "Verified," your drive is in good shape. If it says: "About To Fail" you need to:
1) Not shut down your computer and hard drive until you have completed...
2) Back up your hard drive, which you should do immediately, if you haven't already done so.
Hard drives on their last legs often will finally fail by refusing to start up.

I've been told that there is no hope for an internal drive once it reports "Failing" as its S.M.A.R.T status. Its time to get a new drive.

SMARTReporter is a free application that can automatically warn you of hard-drive failures before they actually happen! It does so by periodically polling the S.M.A.R.T.-status of your hard-drives.
http://homepage.mac.com/julianmayer/

SMARTer is a free utility that reads mounted disks' S.M.A.R.T. status and reports it. You add it to your Mac's login items to have it run regularly.
http://www.euronet.nl/~tekelenb/software/index.html

Note:
FireWire and USB hard drives, even if their internal mechanism is S.M.A.R.T.-enabled, can't be checked for S.M.A.R.T. status.

Discussion.

More information on S.M.A.R.T. technology:
http://www.ariolic.com/activesmart/smart-technology.html
http://docs.info.apple.com/article.html?artnum=88410

http://docs.info.apple.com/article.html?artnum=152349
http://www.storagereview.com/guide2000/ref/hdd/perf/qual/featuresSMART.html
http://en.wikipedia.org/wiki/Self-Monitoring%2C_Analysis_and_Reporting_Technology


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8) CLEAR YOUR DESKTOP
Users have noticed that reducing the number of items on your desktop can noticeably increase the performance of certain activities in OS X. This is easy to do. You can even create one folder on your desktop and put everything on your desktop in it. That will do the trick. Nested items within folders on the Desktop don't count. It is only the total number of items directly on your desktop that matter.
http://www.macosxhints.com/article.php?story=20051117154624368

Another way to go is to put alias' of all of the items that you want to be able to access quickly in a folder; park that folder somewhere other than on your desktop, and then drag that folder to your Dock so that it is always available from the Dock. Whenever you click and hold (or Control-click, or right-click on a two button mouse) on that folder in the Dock, you will be presented with a menu of everything in that folder to choose from. Sort of like the old classic Apple Menu.

Discussion.

Things that you put on your desktop don't really reside there. They actually reside in one of two folders. One folder, called Desktop, can be found at the root level of your computer. Just open your main hard drive icon and it will be there somewhere. The other folder can be found at:
/Users/[your user name]/Desktop
otherwise known as: ~/Desktop, or your user desktop folder.
Open these folders and you will find everything that you see on your desktop!

Apparently the things represented on your desktop use a good chunk of cached memory. It also seems that it is CPU intensive to draw the icons for the things that reside on your desktop. So, moving things to somewhere other than on your desktop is an easy and free way to pick up better performance.


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Lots of folks have problems with Safari bogging down and/or exhibiting the spinning beachball. When this starts to be a problem, there are several things that you can do to fix this.

This hint from MacFixIt, http://www.macfixit.com/, works really well for some:
"...go to /[username]/Library/Safari folder and delete the Icons folder."
This will clear cached favicons (little icons that appear in the address bar).
This tip from OS X Hints will keep this folder from filling up with favicons again:
http://forums.macosxhints.com/archive/index.php/t-36615.html

There are lots of other great hints for Safari maintenance here:
http://www.macosxhints.com/article.php?story=20040324004506941&query=safari%2Bspeed

From MacFixIt:
http://www.macfixit.com/article.php?story=20050921061826456
Under Mac OS X 10.3.x and Mac OS X 10.4.x there exists an issue where some users experience a stall in Safari or other Web browsers when accessing certain Web sites that usually leads to a complete system freeze accompanied by the unending "spinning beach ball" progress indicator.
One solution to this problem is the free utility Unlockupd:
http://www.dshadow.com/software/unlockupd/

A rather extreme, but simple and usually quite effective thing to do to restore Safari to like-new performance is to reset Safari, which will clear Safari's cache and other gunk:
Choose "Reset Safari" from the Safari menu and click "Reset."
http://docs.info.apple.com/article.html?path=Safari/2.0/en/ibr55.html
Note. Resetting Safari clears the history, empties the cache, clears the Downloads window, and removes all cookies. It also removes any saved user names and passwords or other AutoFill data and clears Google search entries. I'm also told that resetting Safari alters your keychain and
bookmarks. For this reason you may want to make copies of the files: ~/Library/Cookies/,
~/Library/Keychains/, and ~/Library/Safari/ so that those can be restored after
resetting Safari.


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9)
RESET SAFARI
10)
REBUILD SPOTLIGHT'S DATABASE
Sometimes, under OS X 10.4, your Macintosh will slow to a crawl, and you can hear that there is a lot of hard drive activity, even though you aren't doing anything disk-intensive with your Mac. To determine what's running in the background, start up Activity Monitor (in Applications/Utilities folder), set it to show "All Processes" and sort by down-arrow "% CPU". That'll show which processes are running, and which, if any, are hogging CPU cycles to the point of drastically slowing down your Macintosh. Look for Dashboard widgets that are hogging CPU cycles. Poorly coded widgets have been known to hog CPU cycles even when you would expect them to be inactive. Uninstall any CPU hogging widgets.

If the culprit is something named "mds" or "mdimport" (the processes that handle Spotlight data), it could signal corruption of your Spotlight database. (Make sure that you aren't just seeing normal Spotlight indexing. See if this problem perseveres after your computer has been left on all day.) If this problem persists, you can easily rebuild your Spotlight database by opening System Preferences, choose the Spotlight panel, click on the Privacy tab, and drag your main drive's icon into the Privacy window. Now highlight your hard drive's icon within the Privacy window and
click on the "-" button (that is, the minus button in the Privacy Window).

Or you could highlight the hard drive icon in the Privacy window and hit the delete key. This will cause the Spotlight database to be deleted and automatically rebuilt. (You won't be able to use Spotlight while its database is being rebuilt.).

After doing this, leave your Mac on for 24 hours and allow Spotlight to index your entire drive uninterrupted.

Some have suggested that it might be a good idea to rebuild your Spotlight database after every time that you update to a new version of OS X (a full "point" release, e.g. 10.3 to 10.4) .


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Note #1) More On Defragmenting Your Hard Drive

As I indicated above, there are those who will tell you that you *never* need to defragment your hard drive, and to some extent they are correct. Certainly the average user, with a hard drive that isn't anywhere close to being full, and using applications that don't require every last bit of performance that can be mustered, won't notice any significant performance gain from defragmenting their hard drive. (Though you may find defragmenting your hard drive to be important if you do disk-intensive work, such as video editing.)

Just about all of the experts agree that there is a Macintosh problem that manifests itself when your Macintosh gets somewhere around 80% full. However, not all of these experts seem to realize that the problem is due to a lack of free contiguous space on your hard drive. As a result, these folks usually advise that you deal with this whole problem by purchasing a new drive when your old drive gets to be about 80% full. That will work, but, personally, when I have a 200GB drive, with 40GB unused, I expect to be able to use that 40GB before I have to buy a new drive. 40GB is a huge amount of space and it seems silly to just give up on it. Frankly, it seems to me that advising that one always keep a ridiculously large amount of free space available on your drive, to assure reliable operation, isn't the best course.

From MacFixIt:
http://www.macfixit.com/article.php?story=20050310003145313
See under: "Make sure you have enough free space on your startup volume"
Realistically, 20 percent of your Mac OS X startup volume should be kept clear in order to achieve best performance and avoid disk problems.

Rob Griffiths, of MacOSXHints.com writes:
Keeping at least 10% of your drive space free is advice that I've followed for quite a few years; I don't know if that figure is too high or too low, but I've never run into any drive-space-related issues using it as a benchmark.
http://www.macosxhints.com/article.php?story=20050714154930216&lsrc=osxh

If a UNIX system employs non VM for memory management (that is, real memory) the issue of swapping is a different beast altogether. This is because when swapping memory out it has to be done in large contiguous chunks (not small pages of 4096 bytes). For this reason it's important that the swap file space on disk be a contiguous set of tracks/cylinders and if possible have a separate data path to avoid interfering with other user i/o activities.
http://www.macosxhints.com/article.php?story=20010613140025184

Apple says that you generally don't need to defragment your hard drive if you are running OS X 10.2 or higher:
http://docs.info.apple.com/article.html?artnum=25668
But then they say: If your disks are almost full, and you often modify or create large files (such as editing video...), there's a chance the disks could be fragmented. In this case, you might benefit from defragmentation, which can be performed with some third-party disk utilities.
Here they say that in some instances defragmenting your hard drive may be necessary:
http://docs.info.apple.com/article.html?artnum=93699
Of course, all of these Apple technical notes seem to be concentrating on the effect of defragmenting on performance, not on reliability.

Apple adheres to the "leave a ridiculously large amount of free space on your drive and then replace your drive when it prematurely begins to hit its head" concept. They admit that defragmenting your hard drive is a good idea, but they will only admit it for those who badly need to do it. (Folks who really give their drives a workout, and those who edit video.) For everyone else they feel that its just fine for them to purchase a new hard drive when they encounter a problem with a lack of free contiguous drive space. As Apple says, modern hard drives are big. Apple knows that for many users it will take a long time for them to fill their drive up to around 80% full, if ever. They aren't about to recommend maintenance that isn't necessary for everyone. In addition, Apple has always been reluctant to admit to users that they might not be able to get along without some third party utility. For instance, under OS 8 and OS 9 Disk Warrior was practically a necessity. But you never heard Apple admit this.

According to one of their technicians, MicroMat feels that under certain circumstances that defragmenting your hard drive is very important, and may be even be critical to preventing data loss, and based on my experience I concur:
http://www.macfixitforums.com/php/showflat.php?Cat=&Board=Forum38&Number=570817&Forum=&Words=MicroMat
%20strongly%20recommends%20that%20you%20always%20leave%20at%20least%2015%5C%25&Match=Entire%20
Phrase&Searchpage=0&Limit=25&Old=3months&Main=570808&Search=true#Post570817

or

http://tinyurl.com/yuqn4

Continuation of discussion on fragmentation by Micromat tech:
http://www.macfixitforums.com/php/showflat.php?Cat=&Board=techissues&Number=620840&page=0&view=collapsed&sb=5&o=31&fpart=1


Other Defragmentation Utilities...and Disk Warrior:

Some manufacturers use the terms "defragmentation" and "optimization" interchangeably. For instance, as far as I can tell, MicroMat does this even though TechTool Pro doesn't really do any optimization when defragmenting your hard drive.
http://www.micromat.com/

Prosoft's Drive Genius
http://www.prosofteng.com/products/drive_genius_info.php
does both file and disk defragmentation, but as far as I can tell, no optimization. However, their advertising seems to use the terms "defragmentation" and "optimization" interchangeably.

Intech Speed Tool's documentation:
http://www.speedtools.com/Users Guides/Disk Defrag Guide.pdf
says that the product defragments your drive, but it does not optimize it. So it would appear that Intech's product is not an optimal choice.

NOTE: Alsoft refers to what Disk Warrior, their popular hard drive repair utility, does as "optimization" and/or "defragmentation", however, they are referring to the drive's directory, not to defragmentation and optimization of the files (data) and free space on the drive. Many folks get confused by the terminology used and think that Disk Warrior is a hard drive defragmentation utility, and it is not. Your Macintosh maintains a "directory" which is an invisible structure that is a catalog of all of your Mac's files and system parts. (It is actually more complex than this simple explanation.) If the directory becomes corrupted your Mac can lose track of what is on your hard drive. (e.g. Your files disappear.)
For a more detailed and technical explanation, see:
http://docs.info.apple.com/article.html?artnum=19516
Disk Warrior fixes your Mac's directory by rebuilding a new optimal one from scratch. Other utilities attempt to fix the directory by patching the directory structure rather than by rebuilding it. Disk Warrior also optimizes the structure of the directory for maximum overall disk performance.

Alsoft's hard drive defragmentation product, PlusOptimizer, is many years out of date, and it runs in OS 9 only. I highly recommend against using this product at this point (assuming that you even can), as it is not OS X-savvy and its use may seriously degrade your hard drive's performance.


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Software mentioned on this site, and where to get it.

Free utilities:

PREFERENTIAL TREATMENT
http://homepage.mac.com/jonn8/as/

"DO I NEED MORE MEMORY?"
http://www.hillmanminx.net/dinmm/index.html

'BACK UP USER PREFS'
http://www.m-t-software.com/software-backup.html

CACHE OUT X
http://www.nonamescriptware.com/forums/index.php?&act=Downloads&CODE=02&id=29

MACJANITOR
http://personalpages.tds.net/~brian_hill/macjanitor.html

ANACRON for Tiger (OS X 10.4)
http://members.cox.net/18james/anacron-tiger.html

ANACRON for OS X 10.2 and 10.3
http://www.alastairs-place.net/anacron.html

SHOWVOLUMEFRAGMENTATION
http://people.freenet.de/amichalak/page1/page1.html

SMARTER
http://www.euronet.nl/~tekelenb/software/index.html

SMARTREPORTER
http://homepage.mac.com/julianmayer/

UNLOCKUPD
http://www.dshadow.com/software/unlockupd/

Free multi-function utilities:

Note: Ordinary users might find some of the options included in typical multi-function utilities confusing and/or intimidating. Even worse, they might find some of them to be dangerous! The following multi-function utilities are fairly easy to use and are unlikely to get anyone in trouble. A multi-function utility may save you time when doing routine maintenance, however, if you don't understand all of the features in the following multi-function utilities, it might be best to stick with single-function utilities.
(Note: There is no need to write and tell me about the dozen or so other multi-function utilities for OS X that are available. I've left out mention of them on purpose for the above reason.)

YASU (Runs cron jobs, clears caches, repairs permissions, updates prebinding, and more.)
http://jimmitchell.org/projects/yasu/
Yasu can take the place of several of the above recommend utilities. I recommend Yasu because it won't get ordinary users in trouble, it is free, and it is quick and easy to use. On the negative side, it doesn't give an estimate for the time it will take to complete a task, and it doesn't give you a log of errors found and repairs done.

MAIN MENU (Provides a menu bar menu for running system tasks, including repairing disk permissions, running maintenance scripts, updating prebinding, cleaning caches, flushing the lookupd cache, rebuild Spotlight indexes, verification and removal of .plist preference files, and more.)
http://mainmenu.xmgfree.com/products.html

Shareware utilities:

MACARONI ($9) (runs maintenance tasks automatically on a regular schedule; not necessary if you have Anacron, or OS X 10.4.3 or later)
http://www.atomicbird.com/

TIGER CACHE CLEANER ($9)
http://www.northernsoftworks.com/tigercachecleaner.html

Commercial software:

DISK WARRIOR
http://www.alsoft.com/DiskWarrior/index.html

TECHTOOL PRO
http://www.micromat.com/tt_pro_4/tt_pro_4.html

INTECH SPEED TOOLS
http://www.intechusa.com/

iDEFRAG
http://www.coriolis-systems.com/iDefrag.php

SUPERDUPER
http://www.shirt-pocket.com/SuperDuper/SuperDuperDescription.html




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If you have any additions to this Web site to suggest, I would very much appreciate hearing your suggestions.
Send them to:
Randy B. Singer, randy@macattorney.com

About The Author:
Randy B. Singer is:

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