Chad Leigh -- Shire.Net LLC wrote: > > On Dec 2, 2006, at 12:06 AM, Ian Collins wrote:
[...] >> 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. > > They are? They are being told that the problems they are having is due > to that but there is no proof. It could be a bad driver for example. Or a bad cable, or a bad controller IC, or a bad cache RAM. Or something. The point is, the entire path from the disk to the main system memory is the error domain. ZFS sits at the top of this domain and thus can detect and correct errors that something lower in the domain can not. >> People >> expect errors form single drives, > > They do? The tech specs show very low failure rates for single drives > in terms of bit errors. Very low. Almost never, perhaps, but not never. Bit errors happen. When they do, data is corrupted. Hence, single drives corrupt data - just not very often and not repeatably at will. So those soft errors are easy to ignore or dismiss as something else. >> so they put them in a RAID knowing the >> firmware will protect them from drive errors. > > The RAID firmware will not protect them from bit errors on block reads > unless the disk detects that the whole block is bad. I admit not > knowing how much the disk itself can detect bit errors with CRC or > similar sorts of things. Actually, some RAID configurations should be able to detect errors as they calculate and check the parity block. >> They often fail to >> recognise that the RAID firmware may not be perfect. > > ZFS, JBOS disk controllers, drivers for said disk controllers, etc may > not be perfect either. Sure. Nothing's perfect. What's your point? ZFS sits on top of the pile of imperfection, and is thus able to make the entire error domain no worse than ZFS, where it is likely much worse to begin with. Dana _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
