Re: backups

On Wed, 30 Jun 2004 18:23:08 -0500, wespvp(at)syntegra(dot)com
<wespvp(at)syntegra(dot)com> wrote:
>
> What do other sites with mondo databases do?
>

Let me offer the ideas of what I've used in some high-end environments
before. First, we've always used a mirror configuration in most
situations, simply for reliability and performance concerns (we can
get into the arguments of RAID-5, but that's neither here nor there).
So, it ends up being 1+0 (mirroring of striped sets).

What you can do is split the mirror and back up one side of the duplex
set. This leaves the database running on the other side, and when you
join them back together, the logs will catch up. This does have a
potential performance problem associated with it, of course, but
backups always do. It really depends on write-percentages.

If you still need high availability when doing backups, I've also used
triplex setups (3 mirrors), so that you still have one left. The
reality is, drive space is cheap, and the ability to pull them off and
do backups that way is very helpful. You can in-fact in an SAN
reattach them to another server for backups.

As someone else pointed out, you do have the issue of sanity of the
files when you do a backup, so given PostgreSQL's current lack of
PITR, I'd likely stop the database, split the mirrors, and restart the
database. I don't know of anyway to coalesce the database and quiet it
for 1 second to do the split.

Chris
--
| Christopher Petrilli
| petrilli(at)gmail(dot)com