Most folks are using nearline storage....
SATA drives on lower end SAN arrays.

Big RAID 5 disksets.

Because of the way backup data is written, fragmentation is apparantly not a 
big deal.
One place where disk excels is if you don't have the data to stream high perf 
tape drives, disk can handle the stop/start of data flow much better, and 
result in a net perf gain.

Paul

> -----Original Message-----
> From: veritas-bu-admin AT mailman.eng.auburn DOT edu 
> [mailto:veritas-bu-admin AT mailman.eng.auburn DOT edu] On Behalf Of 
> Edson Noboru Yamada
> Sent: February 22, 2006 8:47 AM
> To: List Veritas List
> Subject: [Veritas-bu] Backup to disk -- performance?
> 
> 
>       
> Hi,
> 
> We´ve been asked to examine a backup to disk solution (rather 
> than the traditional
> backup to tape).
> 
> It´s clear that restores are so much faster, but one point I 
> still don´t 
> understand it´s about backup performance: LTO2 drives can support
> a throughput like 50 MB/s or even more; serial ATA disks are 
> able to do something similar?
> (even considering issues like file system fragmentation that 
> happens over the time?)
> If disks are really faster, what kind of storage are you 
> considering? Top boxes like EMC Symmetrix
> or those more simple like HP MSA 1000? What RAID level?
> 
> Or backup to disks is really slower?