Re: How to boost performance

On Wed, 16 Jun 2010 18:23:36 -0400
Increasing stripe cache size from the default of 256 should help
immensely.

echo 16384 > /sys/block/md0/md/stripe_cache_size

Be warned that this consumes (^that amount * 4096 * number of disks) bytes
of
RAM. Some benchmarks:

Hello.  Thank you for the quick suggestions!

First I need to correct myself.  I only have the slowdown when writing to
the server.  Reads from the server are usually in the 60-70MB/sec range
regardless of file size.

Prior to the change above, on a 2GB file, I would start off the write (to
the server) at 70MB/sec and end at about 35MB/sec.  CPU usage was at 100%
with the md0 using about 70% CPU and smb using 30% with flush sometimes
jumping in at 30%.  Wait states remained below 10%.  After the change, on
a 2GB file I would start the write at 70MB/sec and end about 55MB/sec
(nice improvement!).

Switched to a 5GB file and the write ended around 35MB/sec.  At the
beginning smbd would star with 50% CPU but gradually go down to 30% with
md0 ramping up to 70% and flush jumping in from time to time at 30%.

This information is all coming from top.  If I should use something else
that will get more accurate readings, please let me know.

With one change my performance greatly increased but I would like to see
more.  Is there anything else I can do?  I'm hoping to get sustainable
60MB/sec writes.  Is that possible?

Thank you if you have read this far!  :)

---
Will Y.


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