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Re: how to prevent filesystem check



On Wed, Nov 29, 2006 at 09:53:34PM -0800, Andreas Dilger wrote:
> > Even if you "mount -oro -text2 $DEV $DIR"?
> 
> Even then, yes.  It is NOT SAFE to access the same block device on
> multiple nodes at one time.  Even with "-o ro" the mount will cause
> the journal to be recovered.

And even with a ext2 filesystem, as the filesystem changes out from
under the kernel (as the system that has the filesystem mounted
read/write makes changes), the system that has the filesystem mounted
read-only will have see inconsistencies caused by some blocks being
cached and some blocks being not cached, and this could result in
security violations (when blocks containing another user are read by
another non-privileged users) and possibly kernel panics.

The only safe way to mount a block device in a shared mode where one
or more of the systems have the shared block device mounted read/write
is to use a cluster-aware filesystem, such as GFS, OCFS2, or GPFS.

						- Ted


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