[Gluster-devel] Scaled down a bit.

Kevan Benson 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...


-Kevan Benson
-A-1 Networks

More information about the Gluster-devel mailing list