dual-ported raid

[Andreas Dilger]

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.