Mailinglist Archive: opensuse (3666 mails)

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Re: [SLE] Maximum swap size
  • From: Hans Witvliet <hwit@xxxxxxxxxxx>
  • Date: Mon, 07 Mar 2005 00:10:19 +0100
  • Message-id: <1110150619.19314.66.camel@xxxxxxxxxx>
On Sun, 2005-03-06 at 19:44, James Knott wrote:

> This was more of a curiousity type question. Also, IIRC, you can have
> multiple swap partitions, so terabyte swap space is now a possibility,
> though I'd imagine exabyte swap is still a while away.
>
> Incidentally, it wasn't all that long ago, that a fried was bragging
> that he had a total (4 or 5 drives) of 1 GB disk space on his OS/2 system!
>

I allready though so,
For most "normal" situations, sysadmins consider swap nowadays more as a
protection meganism against kernel panics.

Used to be different. I recall the days (on a dec vax/vms 780) and
several hundred people working on it, and on piek moments during the
week, most of us were watching which users were swapped out ;-))
At that time "swapped/paged-out" was a fact of life. But since then,
CPU, cache and mem-speed have rissen 1000-fold; while "background"
-memory, or disks in general perhaps 10 or 20-fold.
So the effect of a process being swapped out of main-memory is felt much
more.

At the HP-UX training classes we were told if a system was using swap
intens and for a longer period, one should prepare for several things:
-Complaining users (bad system response)
-Looking for bad code
-Start procedures for buying additional memory

So over-commiting your memory (thus swapping) is something to avoid at
all costs.

Only perfect sense for swapping a processes on purpose, might be in a
cluster environment, to re-distribute cpu-load....

But that's getting OT...


Hans



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