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I'm running 6 320GB SATA drives in a RAID5 configuration on a Gigabyte M59SLI S5. Last week the system started hanging durning array initialization. One of the disks is dead and another has been kicked out of the array to create a new array.

The end result is I have one broken array with four working disks and and 2 missing disks, one broken array with one working disk and five missing disks, and one new disk ready to go.

I'm looking for a solution to merge the two arrays back into a single array so I can rebuild with the new disk.

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If any changes have been made to the disk that was dropped to create a new array, you'll find out how good your backups are because that's almost the only way to get your data back.

I'll be fair... If only a little writing to the second missing disk has occurred, you could probably send the disks to a data recovery expert and get a solid fraction of the original data. Probably.

A RAID5 array that is missing a disk has the reliability of RAID0 and the performance of RAID5. You want to treat a missing disk as a critical failure to be resolved ASAP. Drive to the store if necessary.

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+1. RAID5 allows for ONE disk failure. It sounds like you have TWO failed(or missing) disks at the same time. RAID5 can't save you from that...! – Torben Gundtofte-Bruun Dec 3 '10 at 6:34

You had (past sense) a RAID 5 array, which allows up to 1 drive to fail. You now have two missing drives. That means the array is broken.

If you want to recover it then:

  1. Wipe the array. Rebuild it with working drives. Restore from backup.
  2. Failing up to date backups: Consider point 1. Do you really need that data? If not wipe the array and restore from backups.
    If you really need what was foolishly written to the array while it already had a broken drive, then first make a backup off all data. (A raw disk copy. E.g. with dd. Then try to rebuild the array with the RAIDs BIOS tools. This might take a long time and I am not conviced that the system is fully reliable afterwards. So after recoving any data and backing it up go to step 1.

Also, with 6 drives consider RAID 6. (RAID 5 really is not a good method except if you really need maximum useable space qnd still some backups. It is NOT a backup. It is a useful format for keeping a system up until you can replace a disk. E.g. for a fileserver in a corporate setup which can remain up until 5 PM, after which backups are double checked and a failed drive is replaced).

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