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From Peter Crowther <Peter.Crowt...@melandra.com>
Subject RE: Performance with many small requests
Date Fri, 08 May 2009 13:40:00 GMT
> From: David kerber [mailto:dckerber@verizon.net]
> Also, right now I'm doing a .flush() after the .write() to the log
> file.  Is that usually necessary, other than to avoid losing
> data lines in case of a system failure?

No, other than that.

What disk subsystem are you running on?  Start Performance Monitor and, from Physical Disks,
monitor your disk writes per second.  If it's over 150(ish, depending on the disk) per spindle
in your disk array, you're saturating your disks.

> How would a
> .flush() affect the speed of returning from a synchronized .write()?

It can be significant, as the data has to get to the file.  I'd check the above.  Also, do
you have any battery-backed write cache (BBWC) on the disk subsystem and how's it configured?
 On systems where disk has proved to be the bottleneck, and there are many small pieces of
data being written, I've seen better than a factor of 10 improvement by adding write cache
in this way.

                - Peter

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