Stuart,
> I'm putting together a road map on how our systems can scale as our load
> increases. As part of this, I need to look into setting up some fast
> read only mirrors of our database. We should have more than enough RAM
> to fit everything into memory. I would like to find out if I could
> expect better performance by mounting the database from a RAM disk, or
> if I would be better off keeping that RAM free and increasing the
> effective_cache_size appropriately.
If you're accessing a dedicated, read-only system with a database small
enough to fit in RAM, it'll all be cached there anyway, at least on Linux
and BSD. You won't be gaining anything by creating a ramdisk.
BTW, effective_cache_size doesn't determine the amount of caching done. It
just informs the planner about how much db is likely to be cached. The
actual caching is up to the OS/filesystem.
--
--Josh
Josh Berkus
Aglio Database Solutions
San Francisco