How are you picturing the VTL connected?  Via a storage network (HBAs,
etc.)?  What are the advantages to this compared to a separate backup
net?  

Thanks.
Teresa

-----Original Message-----
From: EMC NetWorker discussion [mailto:NETWORKER AT LISTSERV.TEMPLE DOT EDU] On
Behalf Of Curtis Preston
Sent: Sunday, November 04, 2007 11:24 PM
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Subject: Re: [Networker] VTL or disk cabinet backup

What value do _I_ think that VTLs bring to the table?  In a small
environment, I'm not sure they add much.  (I don't think they subtract
much either.)  In medium-sized environments (one NW server, NO storage
nodes), the addition of dedupe really gives you a reason to move off
JBOD/RAID and onto an intelligent disk device.  In such environments,
most of the midrange dedupe NAS or VTL products will work.  In large
environments (multiple NW servers, storage nodes, perhaps other backup
products as well), I'd say that VTLs win hands down over either standard
disk or dedupe NAS.

Standard disk is MUCH harder to use in large, multi-backup-server
environments because of all the provisioning issues.  You have to create
and manage one or more RAID volumes per backup server/storage node, etc.
You're always going to have volumes that are too big or too small,
creating something else to manage.  You can't easily move backups from
one backup server/storage node to another.  If you have different Oss,
you can't even mount the RAID group/volume you made on OS to another
OS's backup server.  You get no dedupe or hardware compression.  You
will have fragmentation issues if you use them as a permanent storage
device (as opposed to disk staging.)

NAS disk (dedupe or otherwise) doesn't meet the needs of very large
environments either, as many of the servers that need to be backed up
need LAN-free backups.  LAN-free backups mean using a block device, and
today a block device means either standard disk or dedupe VTL.  I've
already said what I thought about standard disk, so that leaves only
VTL.

VTLs can easily be shared between multiple backup servers, storage nodes
-- even applications that don't share -- without creating and managing
individual RAID volumes for each server.  They have dedupe and hardware
compression, and any good dedupe device has worked out the fragmentation
issue as well.

---
W. Curtis Preston
Backup Blog @ www.backupcentral.com
VP Data Protection, GlassHouse Technologies

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