Chad Leigh -- Shire.Net LLC wrote: > > On Dec 1, 2006, at 10:17 PM, Ian Collins wrote: > >> Chad Leigh -- Shire.Net LLC wrote: >> >>> There is not? People buy disk drives and expect them to corrupt >>> their data? I expect the drives I buy to work fine (knowing that >>> there could be bugs etc in them, the same as with my RAID systems). >>> >> So you trust your important data to a single drive? I doubt it. But I >> bet you do trust your data to a hardware RAID array. > > > Yes, but not because I expect a single drive to be more error prone > (versus total failure). Total drive failure on a single disk loses > all your data. But we are not talking total failure, we are talking > errors that corrupt data. I buy individual drives with the > expectation that they are designed to be error free and are error > free for the most part and I do not expect a RAID array to be more > robust in this regard (after all, the RAID is made up of a bunch of > single drives). > But people expect RAID to protect them from the corruption caused by a partial failure, say a bad block, which is a common failure mode. The worst system failure I experienced was caused by one half of a mirror experiencing bad blocks and the corrupt data being nicely mirrored on the other drive. ZFS would have saved this system from failure.
> Some people on this list think that the RAID arrays are more likely > to corrupt your data than JBOD (both with ZFS on top, for example, a > ZFS mirror of 2 raid arrays or a JBOD mirror or raidz). There is no > proof of this or even reasonable hypothetical explanation for this > that I have seen presented. > I don't think that the issue here, it's more one of perceived data integrity. People who have been happily using a single RAID 5 are now finding that the array has been silently corrupting their data. People expect errors form single drives, so they put them in a RAID knowing the firmware will protect them from drive errors. They often fail to recognise that the RAID firmware may not be perfect. ZFS looks to be the perfect tool for mirroring hardware RAID arrays, with the advantage over other schemes of knowing which side of the mirror has an error. Thus ZFS can be used as a tool to compliment, rather than replace hardware RAID. Ian _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
