Date: Fri, 24 Apr 2009 02:51:58 -0400 From: Scott Burns <scott@bqinternet.com> To: Andrew Snow <andrew@modulus.org> Cc: freebsd-fs@freebsd.org Subject: Re: UFS2 metadata checksums Message-ID: <49F1618E.3080208@bqinternet.com> In-Reply-To: <49F10660.201@modulus.org> References: <49F048FB.6000401@bqinternet.com> <20090423195335.521db0a7@kan.dnsalias.net> <49F10660.201@modulus.org>
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Andrew Snow wrote: > > Ideally you would implement complete disk checksumming as a GEOM device. > > Then you could layer geom_mirror on top of it, so that if the checksum > fails and returns EIO, geom_mirror can try the alternate device and > rebuild the one with the bad checksums. > > That will then complete the feature set implemented by ZFS, but for any > filesystem on top of GEOM. > > - Andrew > The geli(8) GEOM class is able to verify sectors (and I believe it returns EINVAL on ones that fail), but with a noticeable performance impact. I could certainly see the use for a GEOM class that just does simple checksumming. If gmirror can then be aware of it, that does provide functionality similar to a ZFS mirror. -- Scott Burns System Administrator BQ Internet Corporation
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