RAM vs Performance, how much is more than enough?

[Paul Ramsey]

Gregor Mosheh wrote:

> I know the OS will use spare RAM for filesystem cache,
> which is always good, but I'm curious as to whether
> there's a noticable difference between serving up just
> MapServer with 256 MB of RAM versus 2 GB.

The answer to your question is right there: yes, there will be a
noticable difference, because frequently used files (like indexes) will
get cached. This is even more try if you have a PostGIS database,
because the database will be more agressive than the filesystem about
making sure that "important" files (indexes) are brough into buffer
cache. The speed differential between RAM and disk hits is so very high,
that more RAM in combination with caching (which every modern OS and
database does aggressively) will make things run faster.

Paul