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Mounting recovered disk image

(@kylegordon)
New Member Customer

Hi folks,

I've been given a RAID0 (!) array to recover what I can, and being a newcomer to OSX I'm having some issues with it.

It was a 2 disk RAID0 array, and one disk has failed in a way that is causing too many I/O errors for OSX or SoftRAID to accept. It was an Appleraid 2.0 array, according to the OSX Disk Utility, and SoftRAID recognizes the disks as such, and as being part of an array, but after a short timeout, it fails to mount.

Using Ports, I've installed ddrescue, and created a copy of both disks on safe storage in order to work with the data. I'd like to now instruct SoftRAID ( or anything else for that matter ) to assemble the RAID array from the two disk images.

On Linux I would use losetup to create a loopback device, and then use mdadm to assemble the array from loopback devices.

Is this at all possible on OSX?

Cheers :-)

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Topic starter Posted : 04/11/2016 9:58 am
(@softraid-support)
Member Admin

If you have dd copies of both disks, pasted onto two new disks, then the volume should be recognizable by SoftRAID, unless too many sectors were unreadable on the failing disk.

reconstructing Disk Utility RAID is difficult if it does not automatically show up, for instance in SoftRAID, as it is pretty undocumented. You may be stuck trying to test different stripe unit sizes for recovery, for example.

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Posted : 04/11/2016 10:48 am
(@kylegordon)
New Member Customer

If you have dd copies of both disks, pasted onto two new disks, then the volume should be recognizable by SoftRAID, unless too many sectors were unreadable on the failing disk.

reconstructing Disk Utility RAID is difficult if it does not automatically show up, for instance in SoftRAID, as it is pretty undocumented. You may be stuck trying to test different stripe unit sizes for recovery, for example.

Good to know, thank you. SoftRAID is telling me the stripe unit size on the affected array is 32KB, so I've got that to work with.

I'm just duplicating the copies I have now, to avoid damaging the originals, and then will try hdiutil in order to make the volumes available to the system.

ddrescue informed me that only about 900KB of the 1TB recovered was unreadable, so... fingers crossed :-)

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Topic starter Posted : 04/11/2016 11:22 am
(@softraid-support)
Member Admin

If SoftRAID is seeing the volume, that is good.

I would try Disk Warrior on it to see what it does. With damaged files, you need to be careful, but you are working on copies of the disks, so Disk Warrior is probably the next best step.

See if SoftRAID shows you:
Volume
Links
Mount point / Disk number
File System (HFS)
Capacity of volume (I.e, 500GB, 150GB available)

Each one is a good sign. Then you may have just directory damage in order to be able to recover.

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Posted : 04/11/2016 2:01 pm
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