*BSD News Article 59621


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From: plm@compi.hobby.nl (Peter Mutsaers)
Subject: Re: 2 swap devices: does it make sense?
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	<4denac$re@vulture.dmem.strath.ac.uk>
In-Reply-To: nbc@vulture.dmem.strath.ac.uk's message of 15 Jan 1996 23:17:32
	-0000
Date: Sat, 20 Jan 1996 07:34:22 GMT

>> On 15 Jan 1996 23:17:32 -0000, nbc@vulture.dmem.strath.ac.uk (Neil
>> Brendan Clark) said:

  NBC> Peter Mutsaers <plm@compi.hobby.nl> wrote:
  >> If I define 2 swap devices, each on a different disk, and I'm doing
  >> heavy disk I/O: will both swap devices be used by FreeBSD 2.1 to
  >> divide the disk I/O over the two disks?

  NBC> Swap devices are interleaved, so the answer is yes. How
  NBC> effective this strategy is would (I imagine) depend on your
  NBC> hard disks; for example, I am unsure how useful two IDE disks
  NBC> would be since CPU time is used by data transfers, but SCSI
  NBC> drives would give a definite improvement. At least, that is, if
  NBC> the world is a fair place ;-)

I have SCSI and now with two swap devices I do notice improvement.
But I see always that on the two partitions about the same amount is
used, even when I'm doing a lot of I/O to /var which is on the first
one.

I would expect in this case that the swap device on the other disk is
used more. Is this not supposed to be true?
-- 
______________________________________________________________________
Peter Mutsaers       |  Bunnik (Ut),     |     "Quod licet bovis,
plm@compi.hobby.nl   |  the Netherlands  |      non licet Jovi."