What does the the reconstruction process of mdadm do exactly on raid10

Posted by Azrael on Server Fault See other posts from Server Fault or by Azrael
Published on 2012-10-29T15:28:17Z Indexed on 2012/10/29 17:04 UTC
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raid

I've got a system with 4 disks set up as raid10. All disks are usable, and mdadm all states them with UUUU.

Due to a recent system crash, the raid is currently reconstruction the raid as it was marked as "not clean," and a reconstruction process was started.

On a closer look smartctl shows problems on one disk:

sd 0:0:0:0: [sda] Unhandled sense code
sd 0:0:0:0: [sda] Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE
 sd 0:0:0:0: [sda] Sense Key : Medium Error [current] [descriptor]
Descriptor sense data with sense descriptors (in hex):
        72 03 11 04 00 00 00 0c 00 0a 80 00 00 00 00 00 
        24 cd 78 d4 
sd 0:0:0:0: [sda] Add. Sense: Unrecovered read error - auto reallocate failed
sd 0:0:0:0: [sda] CDB: Read(10): 28 00 24 cd 75 1e 00 04 00 00

With a research about the reconstruction process, I only found information concerning raid5 but nothing for raid10. Can I replace this problematic disk during the reconstruction process, or will I kill the raid with this?

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