Speaker
Dr
Greig A Cowan
(University of Edinburgh)
Description
The start of data taking this year at the Large Hadron Collider will
herald a new era in data volumes and distributed processing in
particle physics. Data volumes of 100s of Terabytes will be shipped
to Tier-2 centres for analysis by the LHC experiments using the
Worldwide LHC Computing Grid (WLCG).
In many countries Tier-2 centres are distributed between a number of
institutes, e.g., the geographically spread Tier-2s of GridPP in the
UK. This presents a number of challenges for experiments in terms of
the use of such centres, as CPU and storage resources may be
sub-divided and exposed in smaller units than the experiment would
ideally want to work with. In addition, unhelpful mistmatches between
storage and CPU at the individual centres may be seen, which make
efficient exploitation of a Tier-2's resources difficult.
One method of addressing this is to unify the storage across a
distributed Tier-2, presenting the centres' aggregated storage as a
single system. This greatly simplifies the data management for the VO,
which then can access a greater amount of data across the
Tier-2. However, such an approach will lead to scenarios where
anaylsis jobs on one site's batch system must access data hosted on
another site.
We investigate this situation using the Glasgow and Edinburgh
clusters, which are part of the ScotGrid distributed Tier-2. In
particular we look at how to mitigate the problems associated with
"distant" data access and discuss the security implications of having
LAN access protocols traverse the WAN between centres.
Authors
Mr
Andrew Elwell
(University of Glasgow)
Dr
Graeme A Stewart
(University of Glasgow)
Dr
Greig A Cowan
(University of Edinburgh)
