- JFS cache size
- Posted by jmm-list-gn on November 8th, 2004
Hello,
Is any method for determining an optimal cache size for JFS?
I have a lot of RAM, 1.5GiB, and have allocated 64MiB to JFS for cache.
Still there seems a lot of thrashing when many small files are moved
around, like when a mail program starts up.
One of the considerations for CPU cache size is not to make it too big
else the cost of managing it exceeds that benefit of the cache itself. Is
there such a breaking point of disk cache as well?
--
jmm dash list (at) sohnen-moe (dot) com
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- Posted by William L. Hartzell on November 8th, 2004
Sir:
jmm-list-gn wrote:
served to go back and review the issues raised in that thread before you
change the size of the cache from the default.
--
Bill
Thanks a Million!
- Posted by jmm-list-gn on November 8th, 2004
William L. Hartzell wrote:
There were several threads the most recent back in May 2004. The
results were inconclusive. The most informative bit was that JFS uses 10%
or 12.5% of RAM for cache, unless it doesn't.
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- Posted by William L. Hartzell on November 9th, 2004
Sir:
jmm-list-gn wrote:
the deault: /LW:5,20,4 are optimal. Going more would cause write
problems and going less would cause read problem.
--
Bill
Thanks a Million!
- Posted by Aaron Lawrence on November 9th, 2004
Suddenly, jmm-list-gn sprang forth and uttered these pithy words:
bigger the better - lets say 1GB as a first jab. For a desktop, maybe
something like 256MB or 512MB - again depending on what you do with it.
--
aaronl at consultant dot com
For every expert, there is an equal and
opposite expert. - Arthur C. Clarke
- Posted by jmm-list-gn on November 9th, 2004
William L. Hartzell wrote:
values, not cache size.
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- Posted by jmm-list-gn on November 9th, 2004
Aaron Lawrence wrote:
So you're suggesting for a server with 1.5GiB RAM, I should start with
a cache size of 1.0GiB?
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- Posted by Aaron Lawrence on November 11th, 2004
Suddenly, jmm-list-gn sprang forth and uttered these pithy words:
For a files-only server, yes. What else is it going to do with the RAM?
Draw fractal pictures?
If it's running applications, then thats a whole new ball game.
--
aaronl at consultant dot com
For every expert, there is an equal and
opposite expert. - Arthur C. Clarke
- Posted by jmm-list-gn on November 11th, 2004
Aaron Lawrence wrote:
My original question was: Is there a practical limit to the cache size?
You are saying: No, make it equivalent to a RAM disk.
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jmm dash list (at) sohnen-moe (dot) com
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- Posted by Aaron Lawrence on November 13th, 2004
Suddenly, jmm-list-gn sprang forth and uttered these pithy words:
Was it? Sorry, I don't know. I don't see why there should be. So long as
the writeback is set to a reasonable time.
--
aaronl at consultant dot com
For every expert, there is an equal and
opposite expert. - Arthur C. Clarke
