Greg,
I've got to go with William in that there is a lot of information that
is needed to make the qualitative judgments you are up against, but I do have a
couple of points I think are worth making on the technology side:
The following is a copy of a previous response post regarding VTL VS
tape post I made. I hope you find it useful:
<snip>
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.
<snip>
Mark Pinder :
Systems Engineer:
Spectra Logic : www.spectralogic.com
To: veritas-bu AT mailman.eng.auburn DOT edu
Subject: Re: [Veritas-bu] VTL vs. Disk based backups
From: william.d.brown AT gsk DOT com
Date: Wed, 30 Nov 2005 22:06:56 +0000
I think you have got to tell us a bit more about the issue you are trying
to address.
Are you looking to get rid of tape altogether? Or are you looking at
alternatives as a primary backup, with a tape as secondary offsite copy?
Could you use the ability of FalconStor and NetApps to clone data
cross-site, do you have the WAN bandwidth, or do you have just one site?
Are you just trying to fix slow clients?
What kind of DR do you have to provide? - e.g you may absolutely need
tapes ready to send to a DR site, with picking lists per application to
suit your recovery priorities.
Is EMC including Clariion or would using the EMC CDL mean supporting
another disk array type?
Do your NetApps have SnapMirror/SnapVault/OSSV?
Do you have loads to spend? (you don't have to answer that...)
-----
People who do this (and we don't...yet) have very different ways even of
using VTLs. As Charles pointed out, NetApp and NBU 6 are designed to do
some cool things.
William D L Brown
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