Hi John,
in practice, this was not what was happening with ATLAS DC2 in our
experience. btw DC2 happened before the TDR was written.
Cheers,
Simon
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Simon George, Dept of Physics, Royal Holloway college, University of London
Email [log in to unmask] Tel. +44 1784 41 41 85 Fax. +44 1784 472794
On Thu, 6 Oct 2005, Gordon, JC (John) wrote:
> I would be surprised if a knowledgible person in ATLAS had made this
> statement. As I can't be bothered reading their TDR in full I am copying
> in Roger Jones for his comments. I have glanced through it and find the
> following requirements for a Tier2 (I include the whole list for
> interest)
>
> - Medium- or long-term storage for required samples. For analysis work
> these will be mostly AOD but could include some fraction of ESD or RAW
> data for more detailed studies.
> - Transfer, buffering and short-term caching of relevant data from
> Tier-1 and transfer of produced data to Tier-1 for storage.
> - Provision and management of local temporary working space for
> analysis, calibration of development tasks.
> - Database services in agreement with the ATLAS DDM strategy.
> - Prioritization of access to data and computing resources.
> - Accounting for processing and data storage.
> - Publication of the necessary information to be used by the Grid
> services and the ATLAS Production System.
>
> To me, the first three seem relevant. If the fourth implied database
> backup I would expect it to be a dedicated system and not a general
> purpose SE.
>
> Medium and long-term storage seems consistent with my understanding of
> 'permanent' without implying any quality or guarantee of service.
>
> In contrast the ATLAS description of a Tier1 includes the requirement -
> In accepting data from Tier-2, a Tier-1 accepts to store them in a
> permanent and safe way and to provide access to it in agreement with
> current ATLAS policy. This is true for both simulated and derived data.
>
> This seems fairly clear to me, the ATLAS model recognises different
> levels of storage quality and identifies them in T2 and T1. Worth
> talking further with them as to whether they expect these differences to
> be published in the information service.
>
> John
>
>
> > -----Original Message-----
> > From: Testbed Support for GridPP member institutes
> > [mailto:[log in to unmask]] On Behalf Of Simon George
> > Sent: 06 October 2005 13:30
> > To: [log in to unmask]
> > Subject: Re: Reminder of the next UKI meeting - Wednesday 5th
> > October 11:00-12:00 via VRVS
> >
> > Hi John,
> >
> > I also had the impression from the discussion with ATLAS a
> > while ago that they were surprised that our SEs could not be
> > regarded as permanent, high quality, backed up storage. And I
> > also drew the conclusion (as I think did everyone in London
> > Tier2) that the recommended way to flag a SE which is not
> > backed up and could go down for a long time if there was a
> > failure (due to limited manpower at the site) was "volatile".
> > If several of us thought this then there must be something in
> > it, even if it is misguided.
> >
> > To answer you Q: we don't think our SEs are less reliable
> > than everyone else's. Rather, we think other people are are
> > not necessarily advertising the true nature of their site. A
> > Tier1 SE is so different to what a Tier2 site can provide.
> > Some sites my have better support and facilities than others.
> >
> > btw This was in addition to the discussion with ATLAS about
> > whether sites could delete old files.
> >
> > I think we do need ways to distinguish between the differing
> > qualities of SEs. I know for ATLAS, long term availability
> > and uptime are important factors. Disk vs tape (access time)
> > is also important. The way forward should be a quick
> > discussion between sites and experiments of how they would
> > like SEs to be described, then update the Glue Schema,
> > document it and we will fill it in. If there is no forum for
> > this, please set one up!
> >
> > Cheers,
> > Simon
> >
> > --------------------------------------------------------------
> > -------------
> > Simon George, Dept of Physics, Royal Holloway college,
> > University of London
> > Email [log in to unmask] Tel. +44 1784 41 41 85 Fax.
> > +44 1784 472794
> >
> > On Thu, 6 Oct 2005, Gordon, JC (John) wrote:
> >
> > > Would either of you care to spell out why you think your
> > systems are
> > > more unsafe than everyone else's?
> > >
> > > John
> > >
> > > > -----Original Message-----
> > > > From: Testbed Support for GridPP member institutes
> > > > [mailto:[log in to unmask]] On Behalf Of William Hay
> > > > Sent: 06 October 2005 12:36
> > > > To: [log in to unmask]
> > > > Subject: Re: Reminder of the next UKI meeting - Wednesday 5th
> > > > October 11:00-12:00 via VRVS
> > > >
> > > > > Hi John,
> > > > >
> > > > > I have declared my storage 'volatile' and I've done so not
> > > > because I
> > > > > delete files whenever I feel like but because I don't
> > consider my
> > > > > storage safe enough to be declared permanent and if
> > > > something happens
> > > > > I know I've done my duty warning the experiments in advance. If
> > > > > experiments don't exploit the glue schema they should.
> > > > That's why we
> > > > > have an information system.
> > > > >
> > > > > cheers
> > > > > alessandra
> > > >
> > > > Ditto.
> > > >
> > > > William Hay, UCL-CCC Site Administrator, Information Systems,
> > > > EISD,UCL
> > > >
> > >
> >
>
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