Re: postgreSQL on NAS/SAN?

On Tue, 17 Jun 2003, Daniel Seichter wrote:

> Hello Scott,
>
> > RAID5 is fine for a database.  It provides a fair compromise between
> > speed, safety, and economy.  If you need more speed, you might need to go
> > to a RAID 1+0 (or 0+1).
> Ok, well, because a progress-person (not postgresql) said, that it will be
> not good for running a (general, not only progress) database on a RAID5
> System.

It really all depends. If it's a report database with only a tiny
percentage of accesses being write oriented then RAID5 is a great
solution.  If it's primarily transactional with lots of writing, then
RAID5 starts to be less of an attractive option.

Generally, the more drives you throw at a RAID5 the better it will
perform, whereas a simple 4 disk setup under RAID1+0 can usually run quite
fast.

> > running postgresql on a NAS or SAN is quite doable, but you should test
> > your configuration carefully.  Note that many NAS units report write
> > completion upon receipt of the data (i.e. before it's actually written) so
> > you may have data integrity issues should the power go out in the middle
> > of a transaction.
> Ok, then we should use a SAN, if we need to use one.

Or make sure if you use a NAS it isn't set to say it wrote the data before
it actually did.

> > One thing you CANNOT do is allow two postmasters to write to the same data
> > store.  That WILL corrupt your database and cause problems.
> This means, that postgreSQL isn't for configuring clusters? We don't need
> one, but we do not know what the future brings :o(

Currently, any clustering / failover / replication is an add on.  If you
were to want to have two Postgresql servers with replication and failover
between them, they would each need their own data store.  That store could
be on the same storage system, they would just have to be in different
directories.

Each replication solution for postgresql has it's advantages /
disadvantages.  Are you looking more for failover, load balancing, hot
spare?