On 28/06/2012 14:06, Костырев Александр Алексеевич wrote:
- RAID1 pairs, plus some kind of intelligent overlay filesystem, eg md-linear+XFS / BTRFS. With the filesystem aware of the underlying arrangement it can theoretically optimise file placement and dramatically increase write speeds for small files in the same manner that RAID-0 theoretically achieves. (However, still no protection against "silent" single drive corruption unless btrfs perhaps adds this in the future?) not only "silent" single drive corruption problem but as I stated in start of topic - crash of first pair.
Bad things are going to happen if you loose a complete chunk of your filesystem. I think the current state of the world is that you should assume that realistically you will be looking to your backups if you loose the wrong 2 disks in a raid1 or raid10 array.
However, the thing which worries me more with multidisk arrays is accidental disconnection of multiple disks, eg backplane fails, or a multi-lane connector is accidently unplugged. Linux MD raid often seems to have the ability to reconstruct arrays after such accidents. I don't have more recent experience with hardware controller arrays, but I have (sadly) found that such a situation is terminal on some older hardware controllers...
Interested to hear other failure modes (and successful rescues) from RAID1+linear+XFS setups?
Cheers
Ed W