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Re: Max Mount Count



On Wed, Jun 06, 2001 at 05:13:36PM -0600, Andreas Dilger wrote:
> 
> We need to add the LVM/ext3 integration before we can do this.  In 2.4
> the super_operations struct at least has the fields for this, but in
> 2.2 you would need to make the hooks conditional upon LVM support.  I
> will actually have to give this a try before I continue to advocate it
> as a solution, although it _does_ sound nice ;-).

The patches for 2.2 LVM/ext3 to do read-only snapshots already exist,
and I believe have been folded into the LVM CVS tree; the hooks in the
ext3 code have been there since 0.6a or so.  

There are some weird LVM bugs which our NAS folks have been trying to
figure out, but it seems pretty clear they are LVM bugs and not ext3
issues.  

(Basically, read-only snapshots work fine if there's only one physical
volume involved, but if you have more than one PV involved, you have
to shutdown the entire LVM subsystem and bring it back on-line before
the read-only volume is available; if you modified the logical volume
after taking the snapshot, disk space is consumed, and the read-only
copy does reflect the state of the filesystem as of the snapshot; but
it just simply seems to be not available until the LVM is restarted.
The wierd thing is that ext3 with read-only snapshots works just fine
if there's only one physical volume.)

						- Ted





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