Re: PG on NFS may be just a bad idea

On Mon, 2007-10-01 at 10:13 -0700, Josh Berkus wrote:

> > Maybe we need to actively discourage people from running Postgres
> > against NFS-mounted data directories. Shane Kerr's paper cited above
> > mentions some other rather scary properties, including O_EXCL file
> > creation not really working properly.
>
> Wouldn't you be describing a Linux-specific issue, though? And possibly
> kernel-specific?

Possibly, though if you have any specific refutations of the Kerr paper
then it would be a good idea to air them. It isn't enough to just hint
some exist.

> It's hard to reconcile this with the real-world performance of
> PostgreSQL on NFS, which is happening all over the place. Most notably,
> Joe Conway's 20,000 txn/sec.
>
> I *do* think it's an accurate statement that if you're going to use
> Postgres, or any other OLTP database, on NFS you'd better have access to
> a NAS expert. But to say that it's a bad idea even if you have expert
> help is probably going to far.

I can see many papers on database performance on NFS, but I don't see
any discussion of potential reliability concerns. If anybody sits near
an NAS expert, it would be great to have that discussion.

I have found some comments that other databases require "specific
configuration settings to ensure efficient and correct usage" of NFS "to
access NAS storage devices".

--
Simon Riggs
2ndQuadrant http://www.2ndQuadrant.com