The Archive
Centre for Scientific Computing in Aarhus CSC-AA facilitates an
Archive System for user files. The Archive System is run on behalf
of The Faculty of Science, University of Aarhus and CSC-AA.
In principle the Archive System provides a userfilesystem of unlimitted
size. Each user can store large files which automatically will be migrated
to tapestorage. Later, when the user wants the files back, they are
transparrantly restored from tape. This technique is often referred to
as HSM (Hierarchical Storage Mangement). Every file is stored
on two tapes, one is online in the tapelibrary, the other is saved in a
fire-resistive box placed offsite the computerroom.
For CSC-AA users:
For users of CSC-AA's systems (currently the IBM-system Fenris/Sleipner,
the SGI-system Karlsen, the Beowulf-cluster Snehvide, the Intel-cluster
Loke, and a few more) the Archive can be accessed as an ordinary (ie. local)
filesystem through a NFS-mount. All users of these systems have access to the
Archive System as /archive/username. Typically files will be transferred
to/from the Archive by using the 'cp', 'mv' or 'tar' commands:
cd ~/myproject
cp nobelprize.tex /archive/john/
tar cvf /archive/john/results.tar .
For users from NF - The Faculty of Science, AU:
Users from The Faculty of Science, AU, can copy files to/from the Archive
with ftp or scp. With ssh it is possible to login to the Archive and manipulate
files as on an ordinary UNIX system. Non-CSC-AA users must
registrate in order to use the Archive,
and must pay for the media (tapes) used. A 200 GB tape costs ca. 555 dkr
(please remember that all data are kept in two copies).
From IFA (Department of Physics and Astronomy) the Archive can be reached on
the address: arc.phys.au.dk, see
here for details.
Usage and ceveats:
To achieve optimal use of The Archive, files should be at minimum 1 MB, but
preferable much larger. This means that users typical store tar-archives or
zip-archives of a number of files - for example files belonging to a
particular project - rather than storing individual files.
Files lesser that 4 KB will not be migrated to tape at all!
On the other hand, the max. supported filesize is 64 GB (due to a limit in
the IBM JFS filesystem). Filesizes of 5-20 GB are for many reasons optimal
and recommended.
As the Archive is not well suited for "short term storage", files should
remain unaccessed for at least ca. 6 months.
The files in The Archive are not subject to any backup procedure. The files
in the users directories serves as "pointers" to the place on a tape where the
file physically resides. If a file in the userdirectory is deleted,
there is no way to restore it!
The Archive consists of the following hardware components:
The main software components are:
