Re: Checksumming RAID?

[Roy Sigurd Karlsbakk <roy@karlsbakk.net>]

> > To do checksumming (and in particular, recovery), requires higher
> > level
> > knowledge of the data. The filesystem can track when it writes a
> > file,
> > and update metadata (including, if desired, a data checksum) once it
> > knows the file is correctly stored. But I don't think it can
> > sensibly
> > be done at the block device level - the recovery procedure doesn't
> > know
> > what is old data, what is new data, or which bit is important to the
> > filesystem.
> >
> > So I think it can make sense to use a filesystem like ZFS or BTRFS
> > that
> > can do checksumming - that is a reasonable level to add the
> > checksum.
> 
> You'll see CRC in XFS in the future as well. Some of the foundation is
> already laid to allow it, but IIRC it requires an on disk format
> change
> for full implementation. On disk format changes are a big deal and are
> taken with great care. IIRC XFS has only seen one or two in 18 years.

I'm afraid that won't help much either, since it'll only allow for *detecting* the errors, and not *fixing* them (as with ZFS and Btrfs). Or perhaps if XFS can integrate with MD somehow?

Vennlige hilsener / Best regards

roy
--
Roy Sigurd Karlsbakk
(+47) 98013356
roy@karlsbakk.net
http://blogg.karlsbakk.net/
GPG Public key: http://karlsbakk.net/roysigurdkarlsbakk.pubkey.txt
--
I all pedagogikk er det essensielt at pensum presenteres intelligibelt. Det er et elementært imperativ for alle pedagoger å unngå eksessiv anvendelse av idiomer med xenotyp etymologi. I de fleste tilfeller eksisterer adekvate og relevante synonymer på norsk.
--
To unsubscribe from this list: send the line "unsubscribe linux-raid" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html