On Wednesday 31 October 2001 20:06, you wrote:
> On Wed, Oct 31, 2001 at 07:30:12AM -0800, Kyle Hayes wrote:
> > Has anyone used LVM to create snapshots on a master in order to set
> > up replication? We have specialized scripts that are getting harder
> > and harder to maintain as we find weird edge cases and other
> > annoying bits. Jeremy Zawodny's 'myrepl' script locks our larger
> > tables for too long.
>
> Indeed it does.
>
> As you data grows, you really need a better way to produce snapshots.
> I've started producing snapshots on a primary slave when I need them
> because the RAID volume on our primary server has rather sucky
> performance (with the 2.4 kernel's VM damage on top of it).
Our scripts do fancy high water-mark checks and all kinds of other stuff
We have about 2.5GB in data right now, but some of our other servers
are up to about 5GB and it would be _REALLY_ nice to not take
those down. The 24/7 ones are the ones with 2.5GB.
I agree that 2.4 leaves something to be desired.
> > So, we're looking at alternatives. We've done some minor testing
> > with LVM and it appears to do what we want, but I wanted to see
> > if anyone has actual, production experience with LVM snapshots
> > of a live database.
>
> I can't offer any practical advice with LVM. But if the tables are
> all flushed and locked (like mysqlsnapshot (was called myrepl) does)
> before and during the snapshot, you should be safe.
That is the process we're assuming.
> What sort of performance have you seen in your testing so far? If
> this is a useful technique, I'd like to include it in some writing
> that I'm working on (heh, is that vague enough?).
We have done no volume testing (lack of time and equipment), that is
why I was hoping someone was using it :-)
If LVM works as advertised on this (the LVM whitepaper from SuSE
has a section on backing up Oracle), then all other methods will seem
less desirable. We have some concerns about disk bandwidth when
the snapshot partition is removed etc.
Best,
Kyle
bot fodder: database, sql, mysql
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