Does Cyrus benefit greatly from increased FS buffer cache?

[John Widera]

Hi,

Last week we posted to the list for info about running Cyrus on 64-bit
RHEL.  But we also needed to ask a more direct question about caching,
though, and didn't.  So we are now...

That q. is, does Cyrus actually benefit from large amounts of memory in an
environment with just a few thousand users ( <1000 simultaneous sessions)
and, say, up to 750GB of mail spool?

Our plan is to throw 12-16GB at it, with the purpose of vastly increasing
the FS buffer cache (and decreasing I/O).  Or, will that just be a waste
of RAM?

Some indications are that, yes, it does improve performance notably:

http://blog.fastmail.fm/2007/09/21/reiserfs-bugs-32-bit-vs-64-bit-kernels-cache-vs-inode-memory/

Anyone have any specific thoughts?  Is there any other benefit we might
see from large memory allocation in 64-bit architecture?

Thanks,

John Widera
Oakton Community College
Des Plaines and Skokie, IL