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Re: [linux-lvm] How do you mount a snapshot?



On Fri, Dec 08, 2000 at 09:09:57AM -0500, Chris Mason wrote:
> 
> 
> On Thursday, December 07, 2000 22:33:00 -0800 David Gould <dg suse com>
> wrote:
> 
> > On Thu, Dec 07, 2000 at 03:56:11PM -0500, Chris Mason wrote:
> 
> [ snapshots ]
> 
> >> It should work with ext2.
> > 
> > Really? I wonder. Maybe right after a sync before anything gets dirtied,
> > but otherwise, how could the disk image be consistantly, er, consistant?
> > And would not e2fsck have the same issues about writing?
> > 
> > Or did I just wake up pessimistic today?
> > 
> 
> The reason it will not work on reiserfs without the extra API is that on
> reiserfs, sync == commit to log, not commit to disk.  So, there is no way
> over the command line (or in the kernel) to ask the FS to sync to disk,
> even when there is no traffic at all on the FS.
> 
> With ext2, if nothing is going on, you can type sync and have all the
> buffers on disk.  It is at least possible ;-)  It would be better if ext2
> could provide the write suspension hooks as well, but I'm guessing that
> will be done in ext3 first (where the journal already does most of the
> work).

Ok, so we are agreeing, it does not work on ext2 either unless you sync
and do not write between the sync and the snapshot. Doable, but not exactly
"safe".

-dg
 
-- 
David Gould                                                 dg suse com
SuSE, Inc.,  580 2cd St. #210,  Oakland, CA 94607          510.628.3380
"As I've gained more experience with Perl it strikes me that it
 resembles Lisp in many ways, albeit Lisp as channeled by an awk
 script on acid."  -- Tim Moore <moore herschel bricoworks com>,
                      on comp.lang.lisp


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