On Wed, Feb 2, 2011 at 11:03 PM, Scott E. Armitage <launchpad@xxxxxxxxxxxxxxxxxxx> wrote: > RAID1+0 can lose up to half the drives in the array, as long as no single > mirror loses all it's drives. Instead of only being able to survive "the > right pair", it's quite the opposite: RAID1+0 will only fail if "the wrong > pair" of drives fail. AFAICT it''s a glass half-full/half-empty thing. Maybe it's just my personality, but I don't like leaving such things to chance. Maybe if I had more than two drives per array, but that would be **very** inefficient (ie expensive usable space ratio). However, following up on the "spare-group" idea, I'd like confirmation please that this scenario would work: >From the man page: mdadm may move a spare drive from one array to another if they are in the same spare-group and if the destination array has a failed drive but no spares. Given all component drives are the same size, mdadm.conf contains ARRAY /dev/md0 level=raid1 num-devices=2 spare-group=bigraid10 ARRAY /dev/md1 level=raid1 num-device=2 spare-group=bigraid10 etc I then add any number of spares to any of the RAID1 arrays (which under RAID 1+0 would be in turn components of the RAID0 span one layer up - personally I'd use LVM for this) the follow/monitor mode feature would allocate these spares as whatever RAID1 array needed them. Does this make sense? If so I would recognize this as being more fault-tolerant than RAID6, with the big advantage being fast rebuild times - performance advantages too, especially on writes - but obviously at a relatively higher cost. -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
