dual-ported raid

Andreas Dilger adilger at clusterfs.com
Mon Oct 16 18:53:44 UTC 2006

On Oct 16, 2006  12:04 -0500, Jeff Garlough wrote:
> What I would like to do is use one
> normally, and mount the second system read-only to perform backups and
> to rsync the filesystem to another filesystem. When it's mounted
> read-write from another system, will mounting the same filesystem
> read-only cause the journal to be committed at the time it's mounted?

Yes, that is very bad.

> If so, is that a bad thing, that is, will it corrupt the filesystem?

Yes, it can corrupt the filesystem.

> Are journal events handled similar to databases, with regard to transaction
> processing of journal events, or could playing "partial" journal events
> (if there is such a thing) cause corruption?  Is mounting the read-only
> instance as a ext2 filesystem the best solution, or does it matter if
> it's mounted ext2 or ext3 as long as it's read-only?

You can't mount it as ext2.

I would instead use a block-device level backup, like "dump" if you really
need to do it this way.  You are probably better off just doing the backup
from the primary node.

Cheers, Andreas
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.

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