Swap size for large memory machines

[Matt Hardin]

In article <1335 at esquire>  writes:
>What is a reasonable amount of swap space to allocate for a machine
>with a fair amount of memory?
>
>I used to feel (for reasons unknown) that twice as much swap space as
>real memory was reasonable--but does that make any sense when you have
>256 megabytes of memory?

I heard the same story from RTOC (about swap to memory ratio), which was later
strongly refuted. I guess there's no real foundation for that "rule of thumb".
I was told to allocate enough swap so that all processes that would be active
at once could be swapped out. It worked out to about twice the amount of 
physical memory (grin!).

>I'm asking because the standard 'b' partition on Pyramid's layout for
>the 1 gigabyte NEC 2363 drive is 30 megabytes.  That seems a bit stingy
>and I'm wondering what to do about it.  Should I create my own (larger)
>partitions (which I'm doing anyhow for other disks)?

Don't change the partitioning for your system drive. The guy who installed
our system (from Pyramid, no less) did that and it caused me nothing but grief
when the first PTF tape came along and replaced conf.c. Blooey! There went our
modified partitions! It also replaced /etc/disktab (I found out later), 
causing disktab's version of the partitioning to revert back to normal.

What I am doing now is using both the b and c partitions as swap by
issuing a swapon command for each partition (really I just defined partitions
b and c as swap in /etc/fstab, but it works out the same way). This gives us
ample swap space for our machine. What took me by surprise was that you could
issue two or more swapon commands! I get to keep my standard partitions and 
have as much swap space as I need!

>If it matters at all, this is for OSx5.0 on a MIServer.

The folks at Pyramid may have something to say about the performance of this
type of configuration. I know I'd like to hear how it compares to using just
one big swap partition...

				Matt Hardin
				mdh at SR.COM