I started with 5 drives. 1 has failed (i.e. fails to communicate anything) and 2 more are returning read errors. My plan is to use ddrescue to store the 4 working drives to iso files.

After this I can map the iso's to virtual devices, however, how do I force mdadm to scrub the bits even if No md superblock detected on a particular iso file to a seprate drive without attempting recovery of the originals (since the iso's are mounted readonly)?

I have saved the output of mdadm -E for three of the devices, so I know the 'chunk-size' and 'layout'.

  • 4
    You don't have one failed drive, you have three failed drives. That means it's time to go to your backups. – Michael Hampton Jan 12 '16 at 20:54
  • No the drives are only partially failing, only a few sectors are bad on two of the drives, most of the data is intact and accessable. – user5672707 Jan 12 '16 at 20:56
  • I was able to recover all the information by buying extra hard drives to store backup copies of the iso's, at which point even the failed drive started to communicate again and I was able to use ddrescue on it. – user5672707 Oct 31 '16 at 18:34

You can't. If you want md to "scrub the bits" then you have to mount the files read-write.

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