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Re: UFS2 metadata checksums

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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