On Wed, 28 Nov 2007, Kevan Benson wrote:
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.
Ah ha! Ok, tnx.
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...
Ok, that makes sense.
--
-Kevan Benson
-A-1 Networks
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Chris Johnson |Internet: johnson@xxxxxxxxxxxxxxxxxxx
Systems Administrator |Web: http://www.nmr.mgh.harvard.edu/~johnson
NMR Center |Voice: 617.726.0949
Mass. General Hospital |FAX: 617.726.7422
149 (2301) 13th Street |Once technology is our master
Charlestown, MA., 02129 USA |well shall reach disaster faster. Piet Hein
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