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From: mbl900@anusf.anu.edu.au (Mathew BM LIM)
Newsgroups: comp.unix.questions
Subject: More than one swap device ?
Keywords: swap
Message-ID: <1991Mar21.132725@anusf.anu.edu.au>
Date: 21 Mar 91 03:27:25 GMT
Article-I.D.: anusf.1991Mar21.132725
Sender: news@newshost.anu.edu.au
Reply-To: mbl900@anusf.anu.edu.au (Mathew BM LIM)
Organization: Australian National University Supercomputer Facility
Lines: 26

I am the administrator of a soon to be installed Fujitsu VP2200 running
UXP (Fujitsu's SysVR4). I have been trying to plan our file system structure
and swap space allocation. We will have 256 MBytes of physical memory
and perhaps a 32GByte SSU (Solid State Unit - basically a Solid State Disk
drive type thingy). There will be 3 disk controllers, each attached to
two channels and supporting a string of 8 - 16 disks each.

With regard to swap space allocation, if more than one swap device has been
defines, how does Unix (SYSV) decide which to use? Presumably pages cannot be
split between swap areas, or can they? 

The reason I am asking this is to help me decide how many swap areas to
have and if placing them on different disks is good enough or would placing
them on different disk controllers altogether be a much better idea?

It would also be nice to be able to define the SSU to be the "primary"
swap space and the others as "secondary". Each of the secondaries would
ideally be equally active.

Any ideas welcome.

-- 
---
Mathew Lim, Unix Systems Programmer, ANU Supercomputer Facility, ANU, Australia.
Telephone : +61 6 249 2750	| ACSnet   : Mathew.BM.Lim@anu.oz
Fax       : +61 6 247 3425	| Internet : Mathew.BM.Lim@anu.edu.au