Re: Scaled down a bit.

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Chris Johnson wrote:
     Hi again.

     I've scaled everything way back as was suggested.  I'm also using
a dd file read as a test rather than iozone.  I have one brick on the
server mounted on the client, that's it.  Using time dd I get between
260 to 285 MS to read a 24 MB file.  Doing the same thing with NFS I
get about 20 to 30 MS less but I can live with that.

     I tried with and without io-threads on the server end.  No
noticable change either way.  I've read with io-threads is supposed to
do.  I had 8 threads defined.  What does it do and does it make a
different which side it's on, client or server?

io-threads is supposed to speed up serving of files when multiple files are requested at the same time (so dd won't trigger any benefits from it at all, being a single request). I.e. In situations on the server where it would be blocking on new requests until finished with the current request, io-threads allows another thread to handle the request for better response and performance (at least that's how I understand it).

As another email a few days ago stated, io-threads on the client side will have little or no effect.

     I also tried the io-cache on the client side.  MAN does that
work.  I had a 256 MB cache defind.  A reread of my 24 MB file took 72
MS.  I don't think it even bothered with the server much.  I need to
try that on the server.  Might help if a bunch of computer nodes
hammer on the same file at the same time.

Careful with io-cache and io-threads together, depending on where you define it (I think), the cache is per-thread. so if you have 8 threads and a 256 MB cache defined, be prepared for 2 GB of cache use...

--

-Kevan Benson
-A-1 Networks




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