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1576Re: StateDir questions

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  • Josh Chamas
    Feb 2, 2004
      Thanos Chatziathanassiou wrote:
      > I've been monitoring the disk usage in my StateDir for some time now and
      > I've found rather interesting stuff about it.
      > First the basics: it's an nfs shared statedir, used by four web servers.
      > I'm using a ramdisk for it, since using an actual disk for it proved
      > discouraging.
      > Here are the stats:
      > measuring from 30.1.2004 – 18:25:00 to 2.2.2004 – 20:32:00
      > number of disk writes:9728300
      > number of disk reads : 100310

      I can't imagine that these performance metrics are measuring what you
      think they are. There is no way that there is a 97/1 write/read ratio.

      I would consider that your mirrored situation might be buffering/caching
      reads locally, and only writing through, so you only see a small fraction
      of reads. I don't really know enough about the mirroring technologies you
      are using to suggest more, but certainly these numbers are pretty

      When I go to get an example of stats from within MLDBM::Sync ( don't try this a

      > Any idea why things are the way they are and what could/should be done ?

      If you want to get to how an Apache::ASP process does its read/writes to
      the MLDBM::Sync databases, I would fire up the apache web server under
      httpd -X mode ( for apache 1.3.2x ), while running under strace capturing
      the system calls that you are interested in. This assumes you are using
      linux, but I am sure there are other system call trace utilities for
      your OS. This would help isolate the stats from the web server side,
      vs. stats that are particular to your clustering/mirroring software.



      Josh Chamas, Founder phone:925-552-0128
      Chamas Enterprises Inc. http://www.chamas.com
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