Swap size (was Re: [aclug-L] RAM question)

[John Goerzen <jgoerzen@xxxxxxxxxxxx>]

Bob Deep <bobd@xxxxxxxxxxxx> writes:

> The only change you might want to make is to your swap size to follow
> the rule of thumb of having swap that is twice the size of your
> memory....It's unlikely you will need to though because your swap usage
> will decrease with more memory.

Just to expand a bit (you already alluded to this, but...)

This is one reason why I feel this "rule of thumb" (which is often
found in some of the Sam's books about Linux) is not necessarily
valid.  The actual relationship is the opposite: the more RAM you
have, the less swap you need, whereas that rule gives you more swap
when you need less.  Some machines run totally without swap because
they have enough RAM.  I could theoretically run my machine like this, 
but a few times a month, I do need swap, so I have swap anyway.

That said, I don't have a better rule :-(

There are historical reasons for this, dating back to older
less-capable Unices where you could actually have a benefit with a
swap size at least equal to the size of RAM even at the cost of disk
space, but with the typical Linux setup, those considerations aren't
relevant.

> (Some older kernels did had troubble seeing memory over a specified
> size, but I don't remember exactly how big your memory had to be or what
> Kernel versions.. Under 128 Meg should not be a problem.)

I think the value is 64 meg.  On some Compaqs, the value is 16 meg :-)


-- 
John Goerzen   Linux, Unix consulting & programming   jgoerzen@xxxxxxxxxxxx |
Developer, Debian GNU/Linux (Free powerful OS upgrade)       www.debian.org |
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