FYI, Lassi could not cc to the storage list.
Cheers, Olivier.
-------- Original Message --------
Subject: Re: Disabled Castor/Castor load test transfers
Date: Sat, 3 Jun 2006 17:31:14 +0200
From: Lassi A. Tuura <[log in to unmask]>
To: [log in to unmask]
*** Discussion title: PhEDEx Discussions
Hi,
> The iowait we observed happened when we where doing dCache->dCache
> transfers using fts.
>
> You can see the iowait difference between srmcp and fts on this page
> http://www.gridpp.ac.uk/wiki/IC-HEP#Transfer_Tests_2006-02-22
>
> We compared how the data is writen on the disk when using fts or srmcp
>
> http://www.hep.ph.ic.ac.uk/~georgiou/dcache_fts/fts-0.png
> http://www.hep.ph.ic.ac.uk/~georgiou/dcache_fts/srm-0.png
>
> you can see the difference yourself. Basically using fts causes the
> disk to jump when writing while srm doing fine.
Thanks Olivier. Tim Barrass circulated these notes around before, so
we are aware of the situation.
> The transfer rate we could achieve using srmcp (with phedex) was
> close to 400Mb/s while with fts we never reached more than 140Mb/s
> for dcache->dcache transfers.
>
> More tests haven been achieved by configuring the fts channel to
> use srmcp rather than gsiftp third party copy. It improved the
> situation but not dramatically. There will be an upgrade to 1.5 at
> ral next monday and I hope we can make another set of tests.
I understand. We still need to move to using FTS. The weekly WLCG
service meetings are a good place to raise your concerns about the
performance. You should make sure Ian / Micheal / Stefano raise that
issue as they participate in those meetings, but you should be aware
that WLCG is not easily moved by technical facts.
Please do keep in mind that we effectively cannot use srmcp against
Castor/SRM at this time, and most sites do not respond to problem
reports concerning srmcp, or do nothing about them. The reality is
that in practice WLCG only supports the subset of SRM used by FTS.
With RAL moving to Castor you would do well exercise your technical
options earlier rather than later so you can back your position with
clearly articulated numbers.
Lassi
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