Christopher Chan wrote: >> but with RAID 10, data is safe after many types of failures. >> > > Except for the case when a mirror dies after which the whole thing is > toast but in theory you can survive up to four disks going down. > if you have a 8 drive raid1+0, and a random drive fails, you can survive any other drive failing *except* the mirror of the failed one. so if a second drive fails, there's only a 1 in 7 chance that its the 'fatal' one. on a 4 drive raid10, its a 1 in 3 chance. meanwhile, a raid10 can rebuild from a hotspare in like an hour, if the system isn't busy, and a few hours in the background if its busy and active.