[lug] mysqldump versus snapshot versus..

[Zan Lynx]

On Wed, 2007-08-01 at 16:21 -0600, dio2002 at indra.com wrote:
[snip]
> you nailed it.  LVM DOES require table lock on mysql backup.  the benefit
> is that it apparently is a lot faster which only keeps your prod db down
> for a very short time.
[snip]

It *does*?  Whyever?

To the best of my knowledge, an LVM snapshot should look exactly like a
system crash to any application.

If I'm wrong about this, I'd like to know.  Then I'd like to know how
MySQL ever recovers from a system crash. :)

I know that all I do for our system here is LVM snapshot and
rdiff-backup.  PostgreSQL and MySQL have both come back OK from
restores.

Of course, this only holds true as long as the database is only using
storage on the same logical volume.  Snapshots of different LVs can't
happen at the exact same time so there's a possibly skew between the
data tables and the transaction logs if those are not on the same LV.

-- 
Zan Lynx <zlynx at acm.org>
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