Re: Postgres and Ingres R3 / SAN - Mailing list pgsql-performance

Please don't steal threds; post a new email rather than replying to an
existing thread.

On Mon, Mar 06, 2006 at 02:58:32PM -0500, Jeremy Haile wrote:
> Clustering solutions for PostgreSQL are currently pretty limited.  Slony
> could be a good option in the future, but it currently only supports
> Master-Slave replication (not true clustering) and in my experience is a
> pain to set up and administer.  Bizgres MPP has a lot of promise,
> especially for data warehouses, but it currently doesn't have the best
> OLTP database performance.
>
> So, I had a couple of questions:
> 1) I have heard bad things from people on this list regarding SANs - but
> is there a better alternative for a high performance database cluster?
> (both for redundancy and performance)  I've heard internal storage
> touted before, but then you have to do something like master-master
> replication to get horizontal scalability and write performance will
> suffer.

PostgreSQL on a SAN won't buy you what I think you think it will. It's
essentially impossible to safely run two PostgreSQL installs off the
same data files without destroying your data. What a SAN can buy you is
disk-level replication, but I've no experience with that.

> 2) Has anyone on this list had experience using Ingres R3 in a clustered
> environment?  I am considering using Ingres R3's built-in clustering
> support with a SAN, but am interested to know other people's experiences
> before we start toying with this possibility.  Any experience with the
> Ingres support from Computer Associates?  Good/bad?

Can you point us at more info about this? I can't even find a website
for Ingress...

I'd be careful about OSS-based clusters. Everyone I've seen has some
limitations, some of which are pretty serious. There are some that are
command-based clustering/replication, but that raises some serious
potential issues with non-deterministic functions among other things.
Continuent seems to have done a good job dealing with this, but there's
still some gotchas you need to be aware of.

Then there's things like MySQL cluster, which requires that the entire
database fits in memory. Well, if the database is in memory, it's going
to be pretty dang fast to begin with, so you're unlikely to need
scaleability across machines.

Basically, truely enterprise-class clustering (and replication) are
extremely hard to do, which is why this is pretty much exclusively the
realm of the 'big 3' at this point. Slony-II could seriously change
things when it comes out, though it still won't give you the data
guarantees that a true syncronous multi-master setup does. But it will
hopefully offer multi-master syncronous type behavior with the
performance of an async database, which would be a huge leap forward.

Perhaps if you posted your performance requirements someone could help
point you to a solution that would meet them.
--
Jim C. Nasby, Sr. Engineering Consultant      jnasby@pervasive.com
Pervasive Software      http://pervasive.com    work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf       cell: 512-569-9461