jerrymc at clunix.cl.msu.edu
Tue Nov 1 08:00:19 PST 2005
> I just bought 4 servers with 4 gigs of ram, the documentation
> proposes to use 2 to 3 times the amount of ram for swap... I don't
> think 12 gigs of swap would be useful lol, but do I really need to
> put 4 gigs of ram. (It might be useful for kernel dump but...)
> What do you guys do with swap space in this scenario ?
Swap space gets used for at least three things, swapping, paging and
kernel crash dump space. If you are not concerned about dump space,
then the rest of the decision depends a lot on the size and number
of processes you expect to be running at any given time.
Generally, for smaller memory sizes, swap space, via paging gives
you a larger virtual space to run in. But, it looks like you may
by trying to make it so everything gets to stay in memory and never
have any of it paged out, much less swapped out. For our systems
that have plenty of memory, I tend to use about 1 1/2 times memory
for the size of swap - plenty of memory meaning as much as it can
address or at least more than enough to cover all simultaneous
Remember that a lot of utilities and daemons fork off new processes
for each incident they encounter rather than queueing stuff for the
main process to handle. They sort of use it for poor mans queueing.
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