Recently there has been some files disappearing (in iTunes), and I'm not so sure of the extent of this problem yet. Perhaps it may have been an iTunes upgrade bug, but I'm not so sure.

What can I do to check the integrity of the hard drive and of all the files on my Mac computer, to see if they are corrupt or not?

Is there a hard drive integrity checker that I can use on my Mac?


Disk Utility does a very cursory scan of your disk, and should be your first software to consult should you suspect any problems with your disk. Select the option to Verify Disk from the main window. If all tests pass and the drive is marked "OK", but you still suspect a problem (or would like to do a more thorough scan, I suggest picking up SMARTReporter (non-free utility, costs money) and doing a much more in-depth scan.

To run the test, you will have to right click on the disk icon that will be placed in your system tray. Then right click the drive you wish to test and you will see a list of options:

enter image description here

SMARTReporter can perform deeper and more meaningful scans, and can also print specific attributes and thresholds. Below are the results of my OCZ Vertex2 SSD:

Vendor Specific SMART Attributes with Thresholds:
  1 Raw_Read_Error_Rate     0x000f   110   107   050    Pre-fail  Always       -       0/31869480
  5 Retired_Block_Count     0x0033   100   100   003    Pre-fail  Always       -       0
  9 Power_On_Hours_and_Msec 0x0032   100   100   000    Old_age   Always       -       7333h+33m+30.980s
 12 Power_Cycle_Count       0x0032   100   100   000    Old_age   Always       -       89
171 Program_Fail_Count      0x0032   000   000   000    Old_age   Always       -       0
172 Erase_Fail_Count        0x0032   000   000   000    Old_age   Always       -       0
174 Unexpect_Power_Loss_Ct  0x0030   000   000   000    Old_age   Offline      -       10
177 Wear_Range_Delta        0x0000   000   000   000    Old_age   Offline      -       0
181 Program_Fail_Count      0x0032   000   000   000    Old_age   Always       -       0
182 Erase_Fail_Count        0x0032   000   000   000    Old_age   Always       -       0
187 Reported_Uncorrect      0x0032   100   100   000    Old_age   Always       -       0
194 Temperature_Celsius     0x0022   030   030   000    Old_age   Always       -       30 (Min/Max 30/30)
195 ECC_Uncorr_Error_Count  0x001c   110   107   000    Old_age   Offline      -       0/31869480
196 Reallocated_Event_Count 0x0033   100   100   000    Pre-fail  Always       -       0
231 SSD_Life_Left           0x0013   100   100   010    Pre-fail  Always       -       0
233 SandForce_Internal      0x0000   000   000   000    Old_age   Offline      -       2432
234 SandForce_Internal      0x0032   000   000   000    Old_age   Always       -       2880
241 Lifetime_Writes_GiB     0x0032   000   000   000    Old_age   Always       -       2880
242 Lifetime_Reads_GiB      0x0032   000   000   000    Old_age   Always       -       5440

Pay special attention to the Reallocated_Event_Count value, as that is the number of blocks that have been found to be "bad." If you see a high count, that could likely indicate problems with the drive and thus problems with the integrity of your filesystem.

This will give you a better idea as to the health of your current drive.

Should Disk Utility find any problems, repairing the primary partition (that houses your OS) will require a reboot. When you hear the boot chime, hold down the OPTION key and select Recovery HD from the list. Then launch Disk Utility from the menu bar. From there, you can repair your main partition.

  • Thanks for the reply. This is perhaps the best answer so far. A quick question though - if there are problems with the integrity of my filesystem, and I do backups of my installation with Time Machine, would it mean that the integrity of the backup would be bad as well, and as a result, if I restore from that onto a new harddrive, it would have integrity problems?
    – JFW
    Sep 25 '11 at 19:54
  • 1
    No. Bad blocks aren't duplicated or cannot be carried over by TM. They are not "communicable" ;) However, it may mean that some data could have been corrupted. At worst, some of your files may be damaged. It's rare but likely the worst situation you'll face. TM does some verification so it's not something you should lose sleep over.
    – user10355
    Sep 25 '11 at 20:06
  • Ah. Is there any way to fix corrupted data or damaged files? I'd really hate to find out that my photos and writings from a while ago have been corrupted without my knowledge and are now no longer available to me.
    – JFW
    Sep 27 '11 at 19:54
  • Ah. Is there any way to fix corrupted data or damaged files?
    – JFW
    Sep 27 '11 at 19:54
  • Yes. Reboot and hold ALT/OPTION, then select the Recovery HD. From there, you can launch Disk Utility and perform a repair (and a verification as well).
    – user10355
    Sep 27 '11 at 19:58

You can verify the S.M.A.R.T. status of your hard drive at a glance using the System Information utility. (S.M.A.R.T. stands for "Self-Monitoring, Analysis and Reporting Technology.)

enter image description here


You can use the application "Disk Utility" that comes with every Mac. The application lives in your /Applications/Utilities/ folder, but is best when running it off of the Restore Disks that came with the computer. If you restart your computer with the disk in and hold C it will boot to the installer screen. In the menu bar in the top you can choose "Utilities", under there will be Disk Utility. In disk utility I would recommend clicking on the hard drive on the list on the left, then click the "Repair Disk" button on the bottom right. I recommend running the utility off of the CD solely because you aren't checking the files while some files may be in use for the Operating System. This offers the quickest and most reliable verification and potential repair.


My favorite disk maintenance software is probably DiskWarrior. It seems to fix more of my problems than the others. But it's rather spartan in other features. Definitely one to have in your toolkit.

Techtool Pro 6 is a great program. It does close to what DiskWarrior can do, but has all sorts of other features. Including creating a small partition on a hard drive that you can boot into to run maintenance utilities. You can also put other makers' utilities in there. It also has Safari and some other OS X features so you can research problems on the web while fixing. Though they do recommend not running other programs while fixing the boot drive.

DriveGenius 3 is a good one as well with its own set of tools.

But for checking disk integrity specifically, to see if imminent failure is there, all three of them check the S.M.A.R.T. status of your drive. Techtool Pro's S.M.A.R.T. checker is the most comprehensive. It helped me diagnose a whole batch of Maxtor 500 gig drives I had bought about six year ago (about 18 of them) and sure enough, within a few months, more than half of them began failing.

You can also use what's built into OS X. I have found Disk Utility has fixed things none of the others could fix.

And then you can start OS X up in single user mode (Raw UNIX) and check the drive as well. Here's how you do that:

Boot the computer and immediately hold down Command + S.

You'll see text scrolling and then terminal will appear. It gives the instructions I'm about to type right there so you don't have to have it written down.

first you type:

/sbin/fsck -fy

and press enter.

It will run through checks and tell you if the drive appears to be okay, and if it has modified the drive. In the last few versions of OS X, if something is modified it will run the test again automatically. Once it reports the drive appears to be okay, you can go back into standard OS X.

To do that, type:

/sbin/mount -uw /

Hit return



Hit return and it will reboot and start up normally. I use this every time I have a kernel panic or the computer locks up. Though with Lion I have it set to restart automatically if it hangs. So I'm ready to hold down Command + S as soon as I hear the boot chime.

Hope that's not too much information. :-)

  • 2
    FYI: Apple states the following, "Important: If you're using Mac OS X 10.4 or later, you should use Disk Utility instead of fsck, whenever possible.":support.apple.com/kb/TS1417
    – user10355
    Sep 25 '11 at 10:20
  • 1
    Well, that may be true, but you can't run Disk Utility on the boot drive if you're running from the boot drive. Lion creates its own partition for fixing the drive, so that's helpful. Hold Command+R at boot and then choose Disk Utility. Sep 26 '11 at 1:58
  • 2
    Yes you can. You can verify the disk right inside Lion; you just can't repair it unless you boot into recovery mode.
    – user10355
    Sep 26 '11 at 2:32
  • Yes, that is true. Oct 2 '11 at 1:19

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .