[daip] data area optimization

[M.A.W. Verheijen]

Dear AIPS gurus,

I would like to ask your advice regarding the optimization of multiple
data areas (2TB in total) which will be simultaneously accessed by AIPS. 

First a little bit of background.  I have initiated a Large Programme at
the Westerbork telescpe to observe HI in distant galaxy clusters.  For
this, I will fully exploit the new WSRT backend which provides 8 IFs,
256 channels per IF, and 2 polarizations.  Total integration time will
be ~200x12 hours, spread over the coming 3 years.  To accommodate these
data, I am about to order a dedicated multi-CPU data-server with 2 TB of
disk space.  Data processing will probably be limited by data I/O, and
not so much by CPU power. I imagine running multiple IMAGR tasks or
SELFCAL scripts at the same time, accessing multiple AIPS data areas.

I seem to remember that, in AIPS, data I/O benefits from having multiple
physical drives, e.g.  2x250 GB is better than 1x500 GB, given the fact
that AIPS uses temporary scratch files.  The nature of the data (8 IFs)
suggests that is would be best to store the data from each IF on its own
physical hard disk.  Therefore, I thought that having 8 hard disks of
250GB each would be preferred.  These disks would then be RIADed or
(software rsync) mirrored to 8 other identical disks. 

Before investing my money, I would like to ask your advice how best to
configure the 2TB of disk space in order to optimize the data I/O for
AIPS processing, and what kind of hardware this would require.  Would it
be useful to assign part of memory to a (virtual) partition for scratch
files? Would it be advantageous to distribute AIPS data areas or
partitions over multiple hard drives? What sort of RAID system would you
recommend?

Many thanks in advance for any suggestion or comments you can give me.

 Best wishes,

 Marc Verheijen


-- 
*************************************************************************
* Marc A.W. Verheijen                                                   *
* Kapteyn Astronomical Institute    Phone : +31-50-363-4077             *
* Postbus 800                       FAX   : +31-50-363-6100             *
* 9700 AV  Groningen                Email : verheyen at astro.rug.nl       *
* The Netherlands                   URL   : www.astro.rug.nl/~verheyen  *
*************************************************************************