Wednesday, February 22, 2012

Repair Startup Disk with Apple’s Disk Utility

The most obvious benefit that all Mac users enjoy is the ability to perform 'Live verification' of their computer's startup volume using the inbuilt Apple's Disk Utility. However, this feature can be only used with Mac OS X Extended (Journaled)-formatted (HFS+J) volumes. When you run Disk Utility to perform Live Verification, your system may appear slow and some applications may take a longer time than usual to start. If the Disk Utility reports errors, you will have to boot your computer using the Mac OS X bootable DVD and again run Disk Utility to repair those errors.

You may encounter several issues while using Disk Utility. Problems may surface when you attempt to verify or repair an unmountable, non-startup Mac disk. When Disk Utility fails to unmount a non-startup volume during the verification process, it will stop responding and may even halt other system processes. If you see your log files in '/Applications/Utilities/Console', you may observe the following messages:

'The disk “Storage” could not be unmounted
Could not unmount disk for verification
Repairing disk failed with error. Could not unmount disk'   

This generally happens if you have some open files on your disk. If you cannot identify the files that are open, reboot the computer and try to mount the disk again. You can also start the system using Mac OS X Install DVD to perform disk repair.

You may also see another message on your screen while using Disk Utility or 'fsck_hfs' command with '-l' option:

'Incorrect size for file temp'

This happens as the on-disk size for truncated open-unlinked files is not modified before starting with the live verification process. They may not cause any harm because they have a correct in-memory size and hence, can be easily ignored. However, if you repeatedly face such alerts, you can try running 'fsck' in single use mode or boot your system from a different volume prior to verifying or repairing.

In case Disk Utility fails to resolve your issues, you should format the hard drive and reinstall Mac OS X. This process would indeed erase all the data stored on your drive and you might face severe data loss. In such circumstances, you should take help of professional Mac data recovery software.    

Stellar Phoenix Mac Data Recovery is a comprehensive tool that safely recovers your lost files, documents, emails, pictures, music, videos, etc. from all types of Mac hard drives and volumes. The software supports recovery from HFS, HFS+, HFS Wrapper, and FAT file system based volumes. 

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