Problem rebuilding RAID1

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Hi,

I have had a RAID1 array on my NAS520 for a while, a 6TB disk and a 3TB disk. The array was 3TB.

I powered down the NAS, took our the older one of the drives (the 3TB one), plugged in a new 6TB disk - what I wanted was for the new disk to sync with the old one and to then have a 6TB array.

This went as expected, but at the very end of the process the new disk reported it was a 'hot spare'.

I have investigated and see that I have "Current_Pending_Sector" and "Offline_Uncorrectable" are both set to 8 - could this be why the array won't rebuild properly?

Can anyone recommend a way to get the array working properly?

Thanks

J

Accepted Solution

  • Mijzelf
    Mijzelf Posts: 2,638  Guru Member
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    could this be why the array won't rebuild properly?

    Yes. As soon as the rebuilding hits an unreadable sector on the source, it will stop the rebuild, and mark the target as spare.

    Here I wrote about how to solve that for Current_Pending_Sector. It should also work for Offline_Uncorrectable, but in that case the Reallocated_Sector_Ct will increase. So keep an eye on both Offline_Uncorrectable and Reallocated_Sector_Ct. If they keep increasing the disk is dying.

All Replies

  • Mijzelf
    Mijzelf Posts: 2,638  Guru Member
    First Anniversary 10 Comments Friend Collector First Answer
    Answer ✓
    Options

    could this be why the array won't rebuild properly?

    Yes. As soon as the rebuilding hits an unreadable sector on the source, it will stop the rebuild, and mark the target as spare.

    Here I wrote about how to solve that for Current_Pending_Sector. It should also work for Offline_Uncorrectable, but in that case the Reallocated_Sector_Ct will increase. So keep an eye on both Offline_Uncorrectable and Reallocated_Sector_Ct. If they keep increasing the disk is dying.

  • fielden
    fielden Posts: 2
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    That's great, thank you for the information.

    After I posted I rebooted the NAS, since then the array has rebuilt itself and now shows as healthy.

    I may have imagined it, but I think that somehow in the process what was disk1 and become disk2 and vice-versa.

    Does any of that make sense?

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