How to salvage data from a Volume Corruption in Mac?

  • Mac OS X General Volume and Partition information
To know about your Macintosh HD and volumes go to Finder<Application<Utilities and Disk Utilities window. The left hand side of the disk utility windows shows all the partitions along with your Macintosh HD.
  • How to find if a volume is logically corrupted?
Even before the disk utility reports you about the possible logical corruption on the OS X volumes, you can judge by the absurd behaviour of that particular Mac volume. This absurd behaviour may include:
  • Inaccessibility of the Mac volume,
  • The volume may not be formatted or any other operations may not be performed on damaged volume,
  • The volume in disk utility may appear in light shade. This light shaded partition is indication of an unmounted Mac volume. The unmounted drive causes inaccessibility of data that is stored on it.
These are not all but some of the common incidents that begin to show up when one of the Mac volumes goes corrupt. The situation is calculated to be worse when the corruption case is of the boot volume of the OS X Mac. To assure the presence of errors on the OS X volumes go to Disk Utility and select a partition from the left menu. Now, in First-Aid tab click the verify disk to scan volume for errors.

Consider the above snapshot of a Mac volume diagnosed with logical corruption. In a normal scenario the disk utility scans the media and reports the final summary as - . But in an opposite case the disk utility will return each diagnosed corruption with a red line indicating 'danger'. Follow the summary of the 'Verify Disk' process and execute the below places button which is 'Repair Disk'. Many a times the disk utility volume report also indicates faulty disk permissions. So, you have another pair of Verify and Repair Permissions button in the same First-Aid tab. Both of the options can be used to check damaged permissions and ultimately repair them.

Types of logical corruption occurring on Mac partition(s)

It wouldn't be wrong to categorize the types of logical corruption of volume into these phases, namely:
  • Mac boot volume corruption,
  • damaged permissions on OS X,
  • Affliction to caches files and folders.
Most known reasons responsible for logically damaged Mac volumes:
  • The first and the foremost reason for logical damages would be abrupt system shut offs, including hard Mac shut downs,
  • Fallacious applications causing damages to OS X resources,
  • Directory corruption of the volume leads to complete inaccessibility of the data,
  • Although Mac is much secure against malware and viruses but possibility of logical failure of the volume can't be ruled out.
  • Other instances of volume corruption could be summed as – damage to catalog files, overflow extent, faulty journaled, errors in multi-linked files etc.
Types of Failed Volume error messages displayed by Mac OS X:

This error in particular is displayed when the header is corrupted in one of the Mac volumes.

'Volume Header needs minor repair
The volume Macintosh HD needs to be repaired.
Error: The underlying task reported failure on exit
1 HFS volume checked
Volume needs repair'

Initially start with the Disk Utility to repair the corruption, else follow below tutorial.

How to salvage data from a logically failed volume?

If salvaging data is on the priority then here are few tips you can implement to get maximum data out from a corrupted hard drive.
  • Get a demo version of the Macintosh file recovery program. Please careful not to go for a free recovery program as they are inefficient to salvage data from a corrupted hard drive. Yes, they sometimes may recover data which is deleted normally but don't trust such tools for advance operations like recovery from a damaged hard drive.
  • Scan your corrupted hard drive with the data recovery Mac tool & preview the recoverable files from the inaccessible volume. Once you registered for the tool to save the recovered data back to Mac, be careful you choose another destination.
  • In case your boot volume is corrupted then choose a data recovery Mac tool with boot DVD. This boot DVD can be of immense help as it will help you to start the Mac and then scan the boot volume with the file recovery tool. Once all recovered files are previewed you can save them on an external hard drive.  
How to resolve a failed volume?

Above is the case when salvaging data is on your priority. If any how you don't care about the data or you don't have any important data on that volume then you can go for repair first.

Free tips to resolve a corrupt partition on Mac OS X:
  • Jump to disk utility and hit repair disk for the damaged volume. The disk utility will surely resolve errors that are not gigantic in nature. In case the problem is too big for disk utility then follow the next step.
  • Get clone software and an external hard drive.
  • Once you develop a bootable clone media for your Mac you can then perform repair task on the volume with the help of a disk repair utility. This process can also be applied to Mac start-up disk in case of corruption.
How to timely find out a Mac volume corruption?

To timely find out a volume corruption or to prevent a possible corruption, monitor the SMART status of the hard drive. Also, put a habit of verifying and repairing Mac disk on periodic basis.

Let us not ignore some physical damages too?

Yes, a Mac disk is also prone to physical damages. Among most unpopular events of hard drive crashes are the bad sectors. Again, there is no utility present in Mac to figure out no. of bad blocks on the hard drive. You have to turn up to a non Apple utility to check out the presence of bad sectors on the Macintosh HD and partitions.

Once the 3rd party tool reports bad sectors on the hard drive, immediately use a clone utility to copy the media to another media. Don't worry the cloning utility as well as imaging doesn't replicate the bad sectors of the hard drive. It only copies the good and healthy sectors. While doing so you may loose some pieces of data that is located on to the bad sectors of the hard drive. But again you will be able to succeed in salvaging data from the entire hard drive in question.