How do you know if your server needs more RAM
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posted by 2Guns
To know if you need more RAM, run:
vmstat -m 2
(which updates itself every 2 seconds) while the server is busy. The "swpd"
column shows how much swap (in Megs) is being used. Ideally this should be
zero or very close to zero. Also watch the columns "si" and "so" under
"swap", which stand for "swap in" and "swap out." These show how much RAM
the system is having to swap in/out from the hard drive. These should be
zero or very close to zero.
If any of these values are high, your system has run out of physical RAM
and is using swap, which tends to make things run very slowly. Particularly
watching si and so, you can tell how hard your system is swapping if these
values are constantly large and fluxuating.