I have recently tested a DD460 for exactly the same reason. The results
showed that compression was good (upto 20x) but throughput was not so
good. The more clients you add, the slower each backup stream becomes. 
Off course, much depends on your infrastructure, and these results were
based on a windows filesystem, running across a gb network. 
Unfortunately, with millions of small files it is very difficult to
improve performance significantly.
Personally, I could not improve backup or restore performance over an
LTO2 or LTO3 tape drive, and the tape drives still work out cheaper.. so
I decided against it at this time..

Regards

Jon Evans
  



-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Christoph Pilgram
Sent: 16 May 2006 14:43
To: ADSM-L AT VM.MARIST DOT EDU
Subject: Disk-to-Disk Backup

Hi all,

Because we have problems to hold our service level agreements with the
customers for restoring big file-servers (10 Mio files, 1TB disk-space
in one filesystem), we are thinking about storing the backups not
anymore on tape but on disk. Does anybody has experience with that kind
of storage-pool for about 40 TB of backup data ? Does anybody use for
example a "Data Domain DD460" or other systems using COS to reduce the
amount of data.

Thanks for help

Chris 
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