Re: Machine spec 64-bit/32 GB RAM

On Fri, 21 Dec 2007, David Cotter wrote:

> In order to access that 32 Gigs do I have to use 64 bit OS and PG?

Yes. You'll be tormented by various things being limited at 2-4 GB on a
32 bit one.

> Is there any reason not to use a 64 bit?

The only systems I have running 32 bit are because they rely on some
closed-source component where I only have that version available. There
are some wrapper libraries available to work around some of these
situations. Generally, if you're only dealing with open source software,
you should be able to get everything running in 64 bits.

> With a 32-bit version of PG can the 32 G of RAM be used
> for caching?

Yes, but you will have to tune things yourself and ignore a lot of the PG
folklore aimed at earlier versions+smaller machines. I've collected some
guidelines for your sort of situation at
http://www.westnet.com/~gsmith/content/postgresql/ ; the first article
there suggests how to get the database server to use all your RAM
usefully, while the second points out some potential issues with the fact
that by default, your Linux installation may be caching >1GB worth of
writes, which can cause some performance issues when you have a
checkpoint.

--
* Greg Smith gsmith(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD