[PLUG] MySQL v. PostgreSQL -- perhaps an easy answer

[Galen Seitz]

Ian Burrell <ian at znark.com> wrote:

> On Wed, Jan 14, 2004 at 02:39:22PM -0800, Jeme A Brelin wrote:
> > 
> > Which is easier for backups?
> > 
> > I assume that, with either one, you just want to stop the dbms and dump to
> > a file and back that up.  Am I wrong?
> > 
> > I guess this is where y'all tell me I should be using LVM?
> > 
> 
> The on-disk database files can be copied to make a backup only if the
> database server is stopped.  There isn't a mechanism to block clients
> and flush the buffers to disk to put the database in a known state so
> the server must be shut down.  It is possible to make a snapshot by
> copying the database files and transaction logs.  LVM is supposed to
> do this nicely.

To those of you using LVM snapshots, do you really trust the snapshot?
I'm on the lvm-users mailing list, and it seems that snapshot functionality
is a very low priority.  Snapshot questions often go unanswered, and 
to my knowledge, the most recent 2.4 kernel release still doesn't have
all the necessary patches.  Additionally, redhat kernels can't even
mount a snapshot.

One more whine.  In LWM2, the snapshot code isn't finished.

galen