Thread: RAM / Disk ratio, any rule?

hello,

I am wondering if actually, does exists any rule to determine
the amount of RAM, according to the hardware disk size
(in prevision to use all or nearly available space),
when designing a server?

Of course fsm settings implies that when db size grows, more memory will
be in use
for tracking free space.
Same thing applies from RAM cache effectiveness: the bigger db size is,
the more RAM is needed.

Do be more specific, we have an heavy loaded server with SCSI disks
(RAID 0 on a SAS controller),
making a total of 500GB. Actually, there are 16GB RAM, representing
about 2,5% of db size.

any experiences to share?

in advance, thank you.


Mathieu

On Wed, 4 Jun 2008, Mathieu Gilardet wrote:

> Do be more specific, we have an heavy loaded server with SCSI disks
> (RAID 0 on a SAS controller), making a total of 500GB. Actually, there
> are 16GB RAM, representing about 2,5% of db size.

That's a reasonable ratio.  Being able to hold somewhere around 1 to 5% of
the database in RAM seems to common nowadays, and that works OK.  But it's
impossible to have a hard "rule" here because the working set needed to
operate the queries and other activities on your server is completely
dependant on the code you're running, your performance expectations, and
your expected user load.

--
* Greg Smith gsmith@gregsmith.com http://www.gregsmith.com Baltimore, MD