2007/10/26, Greg Freemyer <[EMAIL PROTECTED]>: > On 10/25/07, Ciro Iriarte <[EMAIL PROTECTED]> wrote: > > Anybody has experience with linux Raid5 and power outages?, i > > currently have two 250GB disks in a RAID1 array in my main > > workstation. When there's any power outage the array is rebuilt but > > given it's a mirror it's not a major issue. > > > > Now i would like to add 4 500GB disks in a secondary array with raid5 > > but i'm afraid i would lose the array if there's any outage (have to > > mention a UPS in my letter to Santa....) > > > > Anybody knows if the raid5 (md) would survive this scenario? > > > > The raid should definately survive, but the portion you are writing at > the time could easily be corrupt.
I thought that that kind of corruption would trigger the array rebuild or logical fail... > > Raid5 typically has a 64k per disk data unit, but your issues are > going to really be at the 4k page level I think. > > In particular, when you write/overwrite a page the kernel has to read > the original page of data and the checksum page of data. Update both > and write them both back out. There is really no way the OS can > ensure that both writes actually make it to disk simultaneously. > > So if you have a power outage while writing to a raid5 the odds are > high that one of the 2 updates failed to make it to disk. The good > news, is the array itself should be fine. It just the single raid5 > stripe that is corrupted. You likely won't find out about the problem > until you lose a disk. But even then it will just be a few pages that > are impacted. So?, i will just heal itself?, continue to work with some corrupted files (corrupted stripe effect)? > > Greg > Regards, Ciro -- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
