topic Re: Multiple swaps in Operating System - HP-UX

Multiple swaps

Brando Sumayao — Tue, 13 Nov 2001 15:02:14 GMT

What would be an appropriate size if created multiple swaps on different disks? I have 384mb of physical memory and my primary swap (which I am thinking of leaving alone with a priority of '1') is 768.

I was thinking of creating multiple swap devices of 384mb each spread out on at least 3 disks with a priority of '0').

Thanks.

Re: Multiple swaps

Carlos Fernandez Riera — Tue, 13 Nov 2001 15:09:11 GMT

Yes, you will get a stripped swap ( more or less).

Re: Multiple swaps

harry d brown jr — Tue, 13 Nov 2001 15:10:24 GMT

The more disks the merrier!

live free or die
harry

Re: Multiple swaps

Santosh Nair_1 — Tue, 13 Nov 2001 15:11:44 GMT

Sizing of swap is a tradeoff. It depends on if you're willing to live with some performance penalties with swap rather then buying real memory. But the general rule of thumb (is there one) is that swap should be 1.5 to 2 times the size of physical memory.

That said, its better to spread swap across multiple disks and assign them equal priority. This way when the swap area is needed, the OS can spread the load across the disk rather than using up all the swap on one disk before proceeding to use the next disk.

-Santosh

Re: Multiple swaps

James R. Ferguson — Tue, 13 Nov 2001 15:14:33 GMT

Hi:

A good rule when optimizing device swap is certainly to place them on separate physical disks and make them the same size and of equal swap priority. This allows "round-robin" interleaving of I/O.

That said, I suggest that you quantify your need first:

# swapinfo -tam

Having 3-4 times memory in device swap may not be necessary for your environment.

Regards!

...JRF...