The short answer is there is no way to prevent this beyond being careful.
The difference between xfs and ext2 here is that for an uncleanly unmounted
ext2 partition you need to run a user space application to fix it up (fsck).
For xfs there is no such requirement, the kernel detects the state, and
replays the log to fix up the filesystem.
Unfortunately this does mean that an XFS filesystem will just mount if
you ask it to, which means on a SAN two hosts can mount it at the same
time. There is no way to tell the difference between a filesystem which
crashed and one which is active on another system. We do have logic
to check for the same device already being mounted on the same host
to avoid this very situation there, this depends on an in memory table
though, so cannot be extended to multiple hosts.
Steve
>
> > > > The fact that it is possible to mount XFS partitions in a SAN on
> > > > different machines without any warning led us into some
> > > > problems with
> > > > our servers. Is it possible to check if a partition is
> > > > already mounted,
> > > > without mounting it ;-)
> > >
> > > ehmm..... "mount"? You can mount multiple partitions on the same
> > > mountpoint. it's not an XFS problem but a feature of 2.4
> >
> > I guess he means mounting of a shared disk on more than one
> > computer at
> > the
> > same time. When using ext2 you get the "not cleanly umounted" because
> > the
> > shared filesystem is not marked clean when already mounted on another
> > computer.
> >
>
> Yes, that's exactly what I mean ;-)
>
> Jan
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