[Sorry to be repetitive at the frequency of 1/year]

This is experimental data which is immutable once aquired; read: it does
not change anyore, ever.  It is also not read very often and less so the
older it gets.  It also needs no high-speed access, we have copies of it
in databases for that. 

The costs of keeping it around are roughly: equipment + ops time. 

It appears that particular equipment (netapps filer), which is easy to
operate, becomes too expensive.  It might be a good idea to invest a
little ops time in a cheap storage boxes for stuff that does not need
filer-quality storage.

ATA disks are available at about half a Euro per Gigabute in units of
300GB.  Thus it is possible to put up about a Terabyte of storage in any
simple Wintel box.  Slightly more without redundancy, slightly less with
software RAID.  Any (old) Wintel box will be fine.  The equipment cost
will be negligible: EUR600/terabyte if you use old wintel boxes,
otherwise add the cost of the simplest wintel box.  When building a
couple of them and operating them all the same, the ops cost will not be
too high.  One does not even need RAID.  Just build two of them and have
a cron job rsyncing between them for full hot redundancy.  Name them
cheapfiler-1 and cheapfiler-1-copy, make the copy read-only to users. 
Make as many as we need.  Spread them around for physical redundancy. 

Not rocket science. What's the problem?