[ale] Backup frequency question

[Michael Trausch]

On Tue, 2010-04-13 at 16:07 -0400, William Fragakis wrote:
> Also, does DRBD get around the file lock issue that prevents rsync
> from
> playing well. I would assume it does since it operates at block level
> but I'd hate to assume too much.

I haven't used DRBD yet, but most database systems are able to deal with
a *consistent* PIT snapshot.  It is often possible to take a filesystem
that is providing storage for a database system (and having it running
on LVM, or being a filesystem that provides snapshots itself as part of
the filesystem's functionality) and create a snapshot and rsync that.

Most database systems that I am aware of will be able to see then that
the file lock is stale and do a roll-forward recovery for any
transactions that are pending in the database journal at the time
(assuming, that is, that you're using a fully transactional database
that journals).  With many modern database systems, this shouldn't be
necessary.  Even PostgreSQL starting with the 9.0 release will have
replication support.  Good thing, too, since it seems that many people
that I know are looking to move away from MySQL and the only thing
keeping them from using PostgreSQL is the fact that it doesn't currently
have built-in near-real-time replication.

	--- Mike