Two swap files?

Ari Juhani Huttunen

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May 12, 1996, 3:00:00 AM5/12/96

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I was just wondering... Is it possible to specify two
swap files for OS/2 to use? The scenario I have in mind
is that you have one small but very fast drive for swapping
and if it overflows OS/2 swaps the excess to a slower
disk.

--
--- --
-- -- Ari Huttunen ----
---- -- --
-- ----
--

tom...@swix.ch

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May 13, 1996, 3:00:00 AM5/13/96

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Yeah...
That would be cool...
but can you tell us how to get two swapper.dat... ?
have we just to put the current statement twice in
config.sys ??

Randall Nortman

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May 13, 1996, 3:00:00 AM5/13/96

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In article <nfyg296...@gamma.hut.fi>,

There's no easy way to do this AFAIK. It would be possible, though,
by writing an IFS that was capable of splitting files between two file
systems transparently. The IFS wouldn't have to actually handle disk
I/O, but rather use other IFS's, much the way TVFS does.

Anyway, if such an IFS were created, and it were properly optimized,
then access to the swap file (or any large file, like a database)
could be significantly enhanced. The IFS could keep track of average
seek times and transfer rates on the different drives and split files
between them as appropriate, perhaps even guessing which parts of the
file would likely be accessed sequentially (but weren't sequential in
the file) and place them on different disks to allow simultaneous
seeks.

To my knowledge, such an IFS hasn't been written. And, as I said
before, I don't know any other way to do it (unless IBM implements it
in the kernel for us...) Any IFS programmers out there want to whip
it up, perhaps just a dumb version that just uses the second disk for
overflow? (The smart version I was talking about would be a bit
tougher.)

--
Randall Nortman
The University of Chicago
r-no...@uchicago.edu
http://student-www.uchicago.edu/users/rcnortma

ccr...@pacific.net

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May 18, 1996, 3:00:00 AM5/18/96

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>Ari Juhani Huttunen <Ari.Hu...@hut.fi> wrote:
>>I was just wondering... Is it possible to specify two
>>swap files for OS/2 to use? The scenario I have in mind
>>is that you have one small but very fast drive for swapping
>>and if it overflows OS/2 swaps the excess to a slower
>>disk.

Actually, IBM does very much that sort of thing in its mainframe operating
system (MVS/ESA). Actually, they go a step further by distinguishing between
"swap" and "paging" files. (Swaps are basically just paging operations in which
a large number of pages from the same program are moved in the same operation.

The system automatically balances the load on the various devices, including
taking into account the access speed of the various drives.

Actually, the logic to do this sort of thing is pretty simple. But trying to
incorporate such logic into an operating system for which you don't control
the source code is a bit more difficult.

computer...@concentric.net

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May 19, 1996, 3:00:00 AM5/19/96

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In <DrCzq...@midway.uchicago.edu>, r-no...@uchicago.edu (Randall Nortman) writes:
>In article <nfyg296...@gamma.hut.fi>,

>Ari Juhani Huttunen <Ari.Hu...@hut.fi> wrote:
>>I was just wondering... Is it possible to specify two
>>swap files for OS/2 to use? The scenario I have in mind
>>is that you have one small but very fast drive for swapping
>>and if it overflows OS/2 swaps the excess to a slower
>>disk.

Hey guys just to add a little bit of info
on this, and you may already be aware of it!
But Gama Tech has a compressed power caching tool
for OS2 that is suppose to increase performance.
Since I use a 30 meg swapper and have 32meg of ram
with a newer T-2 board and a 166 a have not looked into it.
But it may be a cost effective way of increasing your hit rate?
Good luck!