Date: Wed, 06 Feb 2008 09:42:51 -0700 From: Joe Peterson <joe@skyrush.com> To: Bakul Shah <bakul@bitblocks.com> Cc: freebsd-fs@freebsd.org Subject: Re: Forcing full file read in ZFS even when checksum error encountered Message-ID: <47A9E38B.6040100@skyrush.com> In-Reply-To: <20080205190946.3D69C5B59@mail.bitblocks.com> References: <20080205190946.3D69C5B59@mail.bitblocks.com>
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Bakul Shah wrote: > It could also be a memory error of some sort. Does your > system haev ECC memory? Yes, I always insist on ECC. > Also note that standalone tests do > not seem to catch all sorts of errors that heavy use of Unix > can sometimes trigger on a marginal system. I do plan to do a few more HW checks (cables, etc.), just to make sure. I had been avoiding touching my HW config to preserve the current state of this issue. However, given the coincidental experience Jeremy talked about and the fact that the DMA errors I have seen using ZFS on FreeBSD that I do not see using ZFS-Fuse on the same disk/pool in Linux, I have a gut feeling something funny is going on. > But I agree with you that it would be useful to have a debug > mode where you can get at the data even if it is bad (and a > test mode where you can write bad data on purpose:-). [A > long rant on writing testable code deleted] Yes, the danger of course is if someone forget's that the debug mode is engaged, but I think care could be taken to make sure this cannot easily be done accidentally or massive warnings can be issues to make sure the user knows. > You have access to the zfs sources! At the very least you can > add code to report the bad checksum & offset and see if > matches with checksum of the same block(s) in your known good > copy. Yep, this is my next planned step. Thanks, Joe
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