VTLs have their place - as long as the current NetWorker licensing model 
doesn't change....
 
The fact that you can present multiple tape drives to a system can have some 
great advantages.  Firstly, you avoid the cost of actually *paying* for all 
those physical drives which you can now add and avoid the headaches when they 
break down (25000 hours MTBF?!?  There goes the theory of relativity...).  The 
additional drives mean that you can present a drive to that remote office which 
takes an entire week to do its full backup and not worry about it hogging a 
drive for the entire time, stream multiple Oracle savesets without laying out 
tons of cash to allow you to recover quickly, save a pile of time unmounting & 
mounting tapes (zero latency on the robot), and generally give a drive to every 
system that's SAN attached.
 
Of course, whether it's viable to do this when your network backups are all 
completing successfully and within window is doubtful, especially if your drive 
maintenance costs are fairly low.  The VTLs also have their problems, mostly 
down to a lack of maturity on the software side.  They should be able to handle 
everything you'd throw at a normal library, but that's not always the case 
(can't remember specific details at the mo, but when an engineer tells you to 
tune your software to present data a specific way, something's fundamentally 
flawed in the way it handles data).  The other biggie is that, given that this 
is controlled by (I'd expect) a single software piece, a "drive failure" could 
mean *all* drives go down that night.  I haven't specifically heard of this 
scenario occurring as yet, but it's not beyond the realms of possibility 
(unlike 25000 hours between failures on a tape drive).
 
This can't be your only backup method though.  Any data which you're offsiting 
will still have to go onto tape, etc.
 
Cheers,
 
Stuart.

 
________________________________

From: Legato NetWorker discussion on behalf of Werth, Dave
Sent: Tue 18-Jul-06 01:58
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Subject: Re: [Networker] Cloning from Disk



This is a little off topic from the original question on this thread but
regarding backup to disk, in anyone out there using a 'Virtual Tape
Library'?  I don't recall seeing them addressed on the list.  It seems to me
you could use one for relatively high speed backups then clone them to a
real tape for offsite disaster recovery purposes.  I gather that they
emulate existing tape libraries so would EMC have any special licensing in
that regard or just treat them like an existing library?

We were considering adding 'Backup to Disk' this year but it appears to me
that a VTL might be simpler and less costly in regards to licensing.  I'd
like to learn more.

Any comments?

Thanks, Dave.

David Werth
Garmin AT, Inc
Salem, Oregon
dave.werth AT garmin DOT com


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