Re: [Gluster-devel] Scaled down a bit.

[Chris Johnson]

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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