disc cleanup

You don't need a defrag utility, the computer and hard drive will function well without this and to some extent they take care of this for you. There are a number of freeware and shareware utilities that can do various maintenance tasks for you, including Onyx (free), Techtool and Disk Warrior (shareware both of which will do some minor defragging) and many more. Mac OS X includes a utility called Disk Utility which will check and/or repair hard drive problems that can result from various situations, but you shouldn't need to use it very often either.

I've been using OS X since about 2003 and have never had a need to defrag my hard drive. I did do some of that in the previous operating system OS 9 from a long time ago, but those were the "good old days".

Hope this helps.

I'm not sure what you mean by "disk cleanup." Defragmentation is done automatically by the OS. In most circumstances, third-party defragmentation tools are not useful.

Whatever you do, don't waste your money on Disk Warrior. If you have adequate backups, which you must have, it's of no use to you whatsoever, despite the misinformation that's spread in these forums.

Linc Davis wrote:

I'm not sure what you mean by "disk cleanup." Defragmentation is done automatically by the OS. In most circumstances, third-party defragmentation tools are not useful.

Whatever you do, don't waste your money on Disk Warrior. If you have adequate backups, which you must have, it's of no use to you whatsoever, despite the misinformation that's spread in these forums.

I was under the impression, DW, which, fortunately, I've never had to purchase or use, was often effective -- numerous reports over the years here suggest -- at repairing directory corruption when Disk Utility failed. A backup as clone might be suffering from the same directory corruption, so don't see how that eliminates the need for something like DW.

Can you please explain why you think DW is worthless.

I was under the impression, DW, which, fortunately, I've never had to purchase or use, was often effective -- numerous reports over the years here suggest -- at repairing directory corruption when Disk Utility failed.

That's undoubtedly true.

A backup as clone might be suffering from the same directory corruption, so don't see how that eliminates the need for something like DW.

A backup would only have the same directory corruption as the original volume if you backed up by doing a block copy with asr(8) or a similar tool -- which would be absurd. A file copy doesn't transfer the volume directory, so the backup would not be corrupted. It might not have all the files that were on the original volume, but Disk Warrior can't do anything about that.

Can you please explain why you think DW is worthless.

I didn't say it was worthless. Clearly, it isn't. It's a specialized recovery tool that you'll never need if you have redundant backups.

Directory damage should be a very rare event with journaled HFS. In particular, it does not result from forcible unmounting of a volume, as in a system crash or a power failure. You often see people saying, "Oh, your system crashed, so you have to run Disk Utility (or Disk Warrior) to repair the disk." Wrong. When the volume is remounted, the journal is replayed and the directory is restored to a consistent state (possibly with some loss of data.) Directory damage can only happen as the result of an I/O error.

I have zero tolerance for unrecoverable I/O errors. If the errors are so bad as to result in irreparable damage to a volume directory, then the device should be replaced immediately. Disk Warrior is of no use in that situation. Even if you choose (unwisely) not to replace the drive, you should erase it and restore from backup. That method is faster, cheaper, and more reliable than trying to fix it with Disk Warrior, and unlike Disk Warrior, it always works and never loses any data.

Good explanation. Thanks.

Journaling has always saved things when I've had an unexpected power cut, so all that fits with my own experience. (In fact, had a power failure just minutes after I wrote that last post, with no problems reported by DU.)

But no merit to the claim, which I've heard here a number of times, that if the disk is being written to at the moment it is suddenly unmounted, corruption can result? Always wondered about that, since I would have thought the disk is almost always constantly being written to.

But no merit to the claim, which I've heard here a number of times, that if the disk is being written to at the moment it is suddenly unmounted, corruption can result?

When a journaled volume is mounted, a flag is set in the volume header showing that the journal is "dirty." That flag is cleared when the volume is unmounted cleanly. If it's forcibly unmounted, the flag remains set. The volume directory will be inconsistent temporarily. Upon remounting, the OS sees that the "journal dirty" flag is set, and the journal is replayed, causing the directory to be restored to consistency. It's not magic; files that were being written at the time may be garbled or lost, but the directory won't be corrupted. Disk Utility (or Disk Warrior) would report no problems found.

About Disk Warrior: about 5 years ago I had a serious problem with my Mac refusing to boot, not recognizing the startup disk. I tried Disk Utility and Techtool Pro, they both reported volume or directory corruption which they could not repair. The solution was to reinitialize the drive, reinstall the OS, and restore my data from a backup. As a last ditch try, the tech who works for my office used Disk Warrior (which to this day he still swears by) and it fixed the problem. What I was told and now understand is that DW fixes directory corruption by rebuilding the volume's directory from scratch in a separate file, rather than attempting to fix the specific instance of data corruption. You then check the new directory against the existing file structure on your Mac. When you tell it to proceed, it replaces the corrupt old directory with a new one. This has never failed to work for me.

Linc Davis is correct that you won't need it very often, this kind of problem might happen once or twice over the life of one computer. But then there is my wife's computer, my three adult children, my friends with Macs,my old MacBook Pro at home. I can tell you from long experience that it will happen eventually (at least until Apple replaces its present ancient disk format structure with a modern one). The dreaded blinking blank disk on the startup screen will announce itself without warning one day. If you don't have the time to go to the Apple Store or otherwise find someone to do it for you, or you're under time pressure, or especially if you don't have a backup (shame on you!) of your drive to restore your data and applications from, having this utility can probably do the job - if it doesn't work, then probably nothing else will.

Suggest you read some of the online reviews.

The solution was to reinitialize the drive, reinstall the OS, and restore my data from a backup.

Yes, that was the solution (well, actually it wasn't -- the best solution was to replace the drive and restore from backup.) So why did you need Disk Warrior? If you're going to say you didn't have a backup, then your anecdote is beside the point. I only said that Disk Warrior was of no use if you have backups.

I've had this discussion with some Disk Warrior advocates who ended up becoming abusive because they simply could not understand the point I was making. It's part of the mythology of the Apple discussion forums that you need Disk Warrior, like you need to "repair permissions" whenever anything goes wrong, or when nothing is wrong.