Re: PostgreSQL clustering VS MySQL clustering

Mitch Pirtle wrote:

> Which brings up another question: why not just cluster at the hardware
> layer? Get an external fiberchannel array, and cluster a bunch of dual
> Opterons, all sharing that storage. In that sense you would be getting
> one big PostgreSQL 'image' running across all of the servers.

This isn't as easy as it sounds. Simply sharing the array among
hosts with a 'standard' file system won't work because of cache
inconsistencies. So, you need to put a shareable filesystem
(such as GFS or Lustre) on it.

But that's not enough, because you're going to be running separate
postgresql backends on the different hosts, and there are
definitely consistency issues with trying to do that. So far as
I know (right, experts?) postgresql isn't designed with providing
distributed consistency in mind (isn't shared memory used for
consistency, which restricts all the backends to a single host?).

--
Steve Wampler -- swampler(at)noao(dot)edu
The gods that smiled on your birth are now laughing out loud.