Re: [gentoo-user] Questions re swap and hibernate interaction on 8 gig machine

[Alex Schuster]

Walter Dnes writes:

>   I just got a brand new custom-built 8 gig machine.  There's an outfit
> in north Toronto that has MSI motherboards with PS/2 ports, so I can
> keep my genuine IBM PS/2 clickety-clack-keyboard; wooooohooooo.  And the
> integrated Intel graphics chip has *BOTH VGA AND DIGITAL OUTPUTS*!

Hooray!

>   Anyhow, I have 8 gigs of ram on the sytem (will obviously be 64-bit
> Gentoo) and I want to know how much swap I need.  The general rule of
> thumb is twice the ram.  In this case, it would be 16 gigs.  I think
> that it may not need swap when up, unless I do some heavy duty stuff.

I think this rule does not scale with todays amounts of system ram. If
your system would need a similar amount of swap, swapping such a lot
would make things really really slow. You could probably live without
any swap, except for the purpose of hibernating to disk.

> My main concern about a swap partition is how much I need for
> hibernate-to-disk to work.  Is there a rule about this, or should I
> simply allocate 16 gigs out of my terabyte drive, and play it safe?

The amount of swap needed is the amount RAM actually being used on your
system, compressed. Add the values of the 'used' fields of Mem and Swap
in your free -m output, divide by two, and that should be somewhere near
the amount you need. Maybe even less if tuxonice frees caches and
buffers. 4GB should be more than enough, I'd think.

But hibernation also works with swap files, so there is no need to set
the exact size already. And I suggest the usage of LVM, this way you can
freely and very easily change the swap size as you like. I never install
Linux without LVM these days, this flexibility makes things so much
easier, and I do not have to care much about partition sizes.

	Wonko