" With RAL moving to Castor " RAL aren't getting rid of their dcache are they?
brian
On 05/06/06, Olivier van der Aa <[log in to unmask]> wrote:
> 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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> --
> - O. van der Aa - Imperial College London -
> - LT2 Technical Coordinator -
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