Take the 2-minute tour ×
Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

I have a 80gb HD in my Mac Mini... but only about 30gb of it is in use. I thought an old 60gb HD would be MORE than enough space. (Since I don't need to keep many duplicate copies of old files. And since the oldest files will delete automatically.)

My Mac said something about a major POSIX error.

Makes it sound like the drive itself is damaged and unusable. Or is it?

Could it have instead meant: "Your HD is just too small". (Even though it is FAR larger than my data.)

share|improve this question
The actual error message would be quite helpful. Also, could you check the system logs in /Applications/Utilities/Console.app for anything interesting? –  Daniel Beck Oct 26 '10 at 11:46

3 Answers 3

An posix error, has nothing to do with the size of the hard drive that you are backing up to. Open the console application in the utility folder and place cut and paste the error here.

But please, please please reconsider your decision on a 160 Gb drive. You want and need backup in depth. Why?

Well, quite simply what happens when the file you need to restore has changed 4 times in 2 months? When did the file get damaged or corrupted? The first save? Second? Third? Fourth?

Please consider the fact that a 1 TB drive (USB, external) is $65-70 dollars USD. I'm not saying that you need a 1 TB drive, but that's not much.

For my recommendations, I typically suggest at least having enough storage for 30-60 days worth of backups. My backups at home with a 1TB drive use to last 6-7 months, until I started moving around 300 GB of data (organizing my downloads)....

For more information, and a related posting... Check here ("How Much Space should I reserve for Time Machine").

share|improve this answer
A file that changes 4 (or 400) times per month? I only need ONE copy of it: The most recent. (But the drive is big enough to store 2-3 copies anyway.) –  Paula Nov 4 '10 at 13:57
.... continued.... Why would I want to keep several OLDER copies of the same file... when I already have several NEWER copies? I would NEVER want to "restore to the older file", and "not user the newer file". (Or do people really do that?) "I lost the Oct 2010 copy, but I have the Sep 2010 copy. But I'll restore the Aug 2010 version instead." Huh? Why in the world would I want to do that???? Maybe you like older/outdated files... but I would ALWAYS restore with the newer file. –  Paula Nov 4 '10 at 13:57
Sorry... just no money to waste on to larger hard drives, that I just don't need... while throwing this drive in the garbage. –  Paula Nov 4 '10 at 13:59
Your making a assumption here, that the newer file is better and usable. For example, let's say you have a 1000 row excel spreadsheet, that you work on a regular basis. Let's say you save it on day 3, 8, 15, and day 25. The next time you open it, it's damaged and/or corrupted. Which backup day should you restore from? What if Day 15 is corrupted as well? Backup in depth is useful, and assuming it's a waste of space is ignoring a feature of modern backups that is extremely useful. Yes, it's not needed for everything... but don't poo-poo it since you don't want to use it. –  Benjamin Schollnick Nov 4 '10 at 19:34

"Even though it is FAR larger than my data". That is what you think.

Please read this: http://ryanblock.com/2008/05/good-folders-to-exclude-from-time-machine-backups/

Also use Disk Utility to verify your disk: support.apple.com/kb/ht1782

share|improve this answer
I'm using a 60gb HD to backup 30gb of data... excluding NOTHING. How does an acticle about "what to exclude" mean that my data is actual larger than I think? –  Paula Nov 4 '10 at 13:51
I included this link because I supposed that you don't know that TimeMachine backups include system files by default; these files can take a lot of space. In other words, you have 30GB of data but your backup will require more space than that. –  gulbrandr Nov 4 '10 at 15:12

I have a 500GB drive in my Macbook, and I'm successfully using a 160GB as a Time Machine backup since I'm only using about 60GB currently. I'd verify that the drive is actually okay; It may be damaged, or simply need reformatted, but I suspect the drive here.

share|improve this answer

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.