[Gluster-devel] Scaled down a bit.
kbenson at a-1networks.com
Wed Nov 28 17:29:02 UTC 2007
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...
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