[Veritas-bu] RE: Backups to disk, your opinion

Hi Greg,
        I'll start by telling you I'm in the tape backup industry as an
SE, so the message you are about to get is biased. :-) 
        Having that out in the open, I find it interesting that you are
considering moving your backups from tape (or creating a new backup
environment) by using a box that pretends that it is tape. 
        I got the following directly from the EMC website at:
http://www.emc.com/products/systems/clariion_disk/ 

<snip>
An alternative to traditional tape-based solutions, CLARiiON Disk
Library integrates low-cost ATA drives, tape emulation software...
<snip>

        Disk manufacturers would love for folks to believe that they can
(read should) eliminate tape from the world. Disk is not (for the most
part) portable. It does not have the scalability of tape (Need space?
Add a tape or add a disk, reconfigure, redistribute data because it's a
raid config, re-label). 
        VTL's (Virtual Tape Library), which is really what EMC wants to
sell you, sound like a great idea. I believe you get the worst of both
worlds (tape and disk) when you buy one. Scalability is sacrificed (disk
issue), it's not portable (disk issue) and it still requires backup SW
and all the management (tape issue).
        I must also agree with Katherine and tell you that the biggest
problem we have is customers being able to keep their LTO-3 drives busy
enough. A lot of our customer's can't rip their data off disk and send
it to tape fast enough. SATA or ATA disks are S L O W compared to an
LTO-3 drive (80MB/sec native), even in a fast raid config.
        The one advantage that disk does have over tape is that is
completes a "file space forward 10,000" command immediately. Please do
remember that this comes with a cost. Electricity and cooling are not
cheap and storage density (how much space in your data center) are worse
for disk than tape. I can put 47.5 TB and 12 Tape drives in one rack
space and this includes the device management console and a color GUI
interface on a 8 inch diagonal touch screen). I doubt disk can match
that. 
        Disk to disk to tape has some advantages for high availability
applications or critical restore environments and this should not be
ignored if you have things that require that level of availability for
restores. However, you will have a heck of a time sending your disk
array offsite in a DR situation. :-)
        Lastly, I'd suggest you go investigate your options and get some
(relatively) unbiased assessments of the pros and cons. I did a search
on www.searchstorage.com for "Tape VS disk" and it gave quite a few
"expert opinion" docs to read. The firs one on the list was entitled
"Toigo talks disk vs. tape" and can be found at
http://searchstorage.techtarget.com/qna/0,289202,sid5_gci839353,00.html.
 
        I hope this helps. Ping me offline if you would like to talk
about it more beyond the group level discussion. 

Mark Pinder
Systems Engineer
Spectra Logic www.spectralogic.com