[asac]Re: Draft of ASAC Report: section on RSC

[Stephane Guilloteau]

Dear Ken,

    I agree with your conclusion, i.e. that a local implementation is likely
to be
much faster than just a portal to the archive. However, I believe we should
leave
the issue opened, and still state that the choice between a "physical copy
or
a link is a matter of LOCAL implementation".  Some RSC(s) may elect to have
a physical copy, other(s) to have just a link. This could be a choice of the
respective user communities.
    Admittedly, if you can afford it, a physical copy probably offers a
better solution to
a strongly concentrated community like in Japan. In Europe, the situation is
different,
and it is yet another case in North America where networks are much more
powerful.

        Stephane



-----Original Message-----
From: K. Tatematsu <k.tatematsu at nao.ac.jp>
To: asac at NRAO.EDU <asac at NRAO.EDU>
Date: Wednesday, April 03, 2002 9:59 AM
Subject: [asac]Re: Draft of ASAC Report: section on RSC


>Dear Pierre, and ASAC members,
>
>At 17:46 02/04/02 +0200, Pierre.Cox at ias.u-psud.fr wrote:
>>We note that the role in supporting archival research overlaps to some
degree
>>with the role of Virtual Observatories and the interaction between the RSC
>>and these VOs needs to be defined. Whether each RSC has a physical copy of
the
>>archive or merely provides a link is a matter of implementation. Various
>>communities have considered  other functions to be important (e.g.,
financial
>>support for the US community, software development for the Canadian
community),
>>but the core functions listed above have been agreed to be the common
>>denominator.
>
>I have a comment on the sentence "Whether each RSC has a physical copy of
the
>archive or merely provides a link is a matter of implementation."
># Although I said the same in the face-to-face meeting, I am afraid that
>most of you
># did not understand my comment.
>
>Let's think about doing archival astronomy by using VO.
>Ten years later, we will have local ALMA archive (physical or link) and
>Subaru archive in Tokyo.
>If you believe in Moore's law in computing, the network speed will be of
>order 100-1000
>times faster than the present day in 10 years.
>So, local network speed (within NAOJ and directly connected universities)
>would be of order Tbps (now 1-10Gbps), while global network
>between Tokyo and Chile (or USA or Europe) would be of order Gbps (now
>1-10 Mbps).
>
>Some astronomer may try to do VO astronomy (without using pre-existing
simple
>catalogues) to get brand-new result by cross-correlation.
>We assume that he/she likes to cross-correlate the ALMA and Subaru
database.
>You know that yearly ALMA data amount can be
>of order 1 PB, and the archive is very large in size.
>
>If the ALMA archive is physical in Japan, cross-correlation on network is
>very fast on Tbps
>network. On the other hand, if the ALMA-J archive is just a link to Chile
main
>archive, cross-correlation is 1000 times slower, because it uses Gbps line.
>
>Even for a USA archive researcher has benefit from high-speed link between
>the ALMA-J physical archive and Subaru archive.  Cross-correlation
>will need high-speed network between archives, while the result
>can be sent to USA even on slower Gbps line because the data size of
>cross-correlation is much smaller.
>
>Here, I assume that cross-correlation is not CPU-power bound
>(e.g. position of two data archive is well determined, and image matching
>is not necessary
>...)
>
>I feel that whether the local archive is physical or just a link is not an
>implementation
>issue but more serious if we mind how quick we can get scientific result.
>Or, you can wait for 1000 times longer time...
>
>If I miss the point, please let me know it.
>
>Cheers,
>Ken
>
>
>
>
>
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