Kris,

        Your general understanding of how VTL works is  pretty much correct.
 There are certain advantages to VTL which you have not mentioned such as "out
of the back end duplication" but if you need to keep an image on-site as well
as physical tape off site at the same time then you got it.  As far as whether
to make any SAN attached host a media server depends entirely on your
configuration and what you need to back up off of these hosts.  If the amount
of data is trivial, then it may be more efficient to back them up over the
network.  You also need to consider that VTL, just as a physical tape library,
would require a separate SAN connection(s) for the tape drive(s) apart from
your existing SAN connections to the disks.

        Depending on your configuration, you might consider using fewer
robotics contorol hosts (you can have different drives in a single robot
attached to multiple hosts).  In our scenario it works great because we a)use
centralized duplication and b)have clusered robotics control hosts so our
chances of having a downed robot is very low.

        Again, it all depends on what you are tring to do, what you currently
have and how much you are willing to spend.

paulg

        Save On Jan 27,  8:33pm, Williams, Kristopher L wrote:
> Subject: [Veritas-bu] Virtual Tape Library / Drives
> Hello all,
>
>
> I'm trying to get my head around exactly what and how a virtual tape
> drive system works.
>
> Here is how I see it: VTL is mostly a software product that allows me to
> create virtual libraries and tape devices. I can then present those
> devices to any host connected to the FC SAN. (I know that some offer
> iSCSI but I only want to deal with Fiber in my example). Those virtual
> tape drives get written to by NetBackup just like normal tape drives,
> but the data really is stored on a central disk subsystem. Using NB
> duplication, I can get the data off to real tapes to be vaulted for DR
> purposes.
>
> I guess the first idea that comes to mind is to place a virtual drive on
> every SAN attached host and make them all SAN media managers (I know
> that Veritas License Cost will make this sound crazy). I could then have
> each SAN Media server write it's own data to it's local "Virtual" tape
> drive.
>
> Can someone who has a VTL system fill in the holes for me? I'm sure
> there are many many more considerations but I'm just at the thinking
> phase.
>
>
> Thanks,
>
> Kris
>
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>-- End of excerpt from Williams, Kristopher L