On 21/12/17 23:14, Lew Wolfgang wrote:
On 12/21/2017 03:07 PM, Wols Lists wrote:
On 21/12/17 22:55, Lew Wolfgang wrote:
On 12/21/2017 01:22 PM, Wols Lists wrote:
If you've got raid-6 you can recover from any single-disk corruption/failure - just make sure you run regular scrubs to detect it. One tiny correction: with RAID-6 you can recover from any two failed disks. RAID-5 allows recovery from any single-disk failure.
Yes but :-)
Raid 5 will not let you recover from corruption. Raid 6 will, but only one disk ...
Please explain, you lost me there.
Raid 5 has one parity disk. It will therefore let you reconstruct one piece of missing information. If you know disk 2 has failed, you can reconstruct the contents. Raid 6 has TWO parity disks, so you can reconstruct TWO pieces of missing information. If you know disks 2 and 5 have failed you can reconstruct them both. But if you know ONE drive (but you don't know which one) has had a hiccup and corrupted your data - maybe a write got lost, maybe (and this apparently does happen) the drive firmware wrote a block in the wrong place, you can also reconstruct that! You can work out which drive has been corrupted (the first piece of missing information) and what the data should have been (the second piece of missing information). There's a program (raid6check, iirc) which will recover that for you. Cheers, Wol -- To unsubscribe, e-mail: opensuse+unsubscribe@opensuse.org To contact the owner, e-mail: opensuse+owner@opensuse.org