[Gluster-devel] Scaled down a bit.

Chris Johnson johnson at nmr.mgh.harvard.edu
Wed Nov 28 17:41:54 UTC 2007

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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