On Fri, January 23, 2009 09:52, casper....@sun.com wrote: >>Which leaves me wondering, how safe is running a scrub? Scrub is one of >>the things that made ZFS so attractive to me, and my automatic reaction >>when I first hook up the data disks during a recovery is "run a scrub!". > > > If your memory is bad, anything can happen. A scrub can rewrite bad > data; but it can be the case that the disk is fine but the memory is > bad. Then, if the data is replicated it can be copied and rewritten; > it is then possible to write incorrect data (and if they need to recompute > the checksum, then oops)
The memory was ECC, so it *should* have mostly detected problems early enough to avoid writing bad data. And so far nothing has been detected as bad in the pool during light use. But I haven't yet run a scrub since fixing the memory, so I have no idea what horrors may be lurking in wait. The pool is two mirror vdevs, and then I have two backups on external hard drives, and then I have two sets of optical disks of the photos, one of them off-site (I'd lose several months of photos if I had to fall back to the optical disks, I'm a bit behind there). So I'm not yet in great fear of actually losing anything, and have very little risk of actually losing a LOT. But what I'm wondering is, are there known bugs in 101b that make scrubbing inadvisable with that code? I'd love to *find out* what horrors may be lurking. -- David Dyer-Bennet, d...@dd-b.net; http://dd-b.net/ Snapshots: http://dd-b.net/dd-b/SnapshotAlbum/data/ Photos: http://dd-b.net/photography/gallery/ Dragaera: http://dragaera.info _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
