Not to stir up trouble here, and perhaps I should have started another thread
entirely, but all of this talk about VTL had me thinking...
VTL: Why? Who ever thought emulating a device was a good idea? -Emulation is
typically not as good as either the original or especially a complete redesign
of the process.
Best reason for *not* using a VTL: Cost.
Unless things have changed drastically in the past few years, VTLs are and
always will be much more expensive than a tape library for equivalent bandwidth
and storage. Stop and think about this... There are plenty of sites out there
today that still have StorageTek L700 or an older type library in house. Some
of these are over 10 years old now, the tape technology has been updated, and
the tapes themselves in a lot of cases, but one of the most expensive
components remains the same for far longer than you will *ever* see a VTL last.
Depending on the type of disk, I believe these are rated to 3-5 years, for 24
hour operation of non fibre disks.
Assuming you sized things correctly, in a few years time, your VTL will be
outgrown by either capacity or bandwidth. Will you be able to upgrade it? No.
Like any disk system, eventually forklift replacement is your only option. This
doesn't even begin to address the costs of training, documentation, etc.
involved. This also doesn't even consider the fact that in most cases, you
won't be getting rid of your tape library entirely, you'll just be adding
another component to your infrastructure. -Which as we all know more components
can mean more potential problems and more expense as you cannot do long term
backup storage on a VTL without breaking your wallet. (yes DataDomain and
others have some good dedup products, but this is still not an offline, long
term (1+ year) solution) for most cases.
So, why would you use a VTL? Well, for the same reasons you'd use a disk.
-Slightly faster in *some* cases depending on the type of workload being sent
to it. But honestly, again, why use a VTL for this? There's a much better
solution.. Disk.
And I'm not talking AFTD (which based on the discussions I've been reading
through here "advanced" file type device is a bad joke to say the least). I'm
talking *snapshots* and *replication* to disk. There are plenty of different
brands of this, host based, network based, filer based, etc. So what do you get
here? The same things you get with a VTL, only better, and cheaper.
Snapshot technologies give you incremental change backups - online and
restorable by the *user*. -Tired of doing hundreds of individual file restores
a day? Make your users do them themselves and save yourself the headache. They
know what they are looking for, and where to find it better than you ever will
(well, in most cases ;-) How much space do snapshots take up? Not much at all.
Obviously this depends on the type of data, but in my experience 10-12% daily
change rate is about all you will ever see for My Document type file changes.
Changes done at the block level, are a lot less than that. Ask yourself this,
how many .doc or .xls files do you have right now, and how many have you
*touched* today?
Mirroring technologies give you DR capabilities that a VTL does not. Want that
Oracle database up 24/7? You'll need a second site with mirroring setup or you
are looking at some downtime in a disaster. Also remember, if you mirror to a
second site, you can then backup your secondary location to tape whenever you
want without impacting your customer and your tapes are already shipped offsite
from the primary data.
So, keeping these two technologies in mind, can someone explain to me a
situation where you could honestly say a VTL is required over other disk
technology, or where it is cheaper than other disk technology? Or for that
matter, the same questions for a properly populated tape library vs. a VTL.
Thanks,
Will
PS - I decided this is *on topic* as any of these technologies would require a
backup solution at the end of the day, but using these other technologies
basically changes the face of most Networker environments.
I would also like to put out there an open question to anyone using these types
of technologies in a Networker environment that cares to explain their basic
setup. e.g. primary and secondary site filers mirrored, then backed up with
Legato NDMP to tape for example. -Mostly a curiosity question here as I'd like
to see how others are taking advantage of these technologies using Networker in
the mix.
-----Original Message-----
From: EMC NetWorker discussion [mailto:NETWORKER AT LISTSERV.TEMPLE DOT EDU]On
Behalf Of Curtis Preston
Sent: Thursday, August 21, 2008 2:04 PM
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Subject: Re: [Networker] Query in Staging from adv_file
>I don't think device count is relevant in a NetWorker environment
>because EMC doesn't license anything based on device count.
That's not entirely true. First, there are versions of NetWorker where
you're only allowed to have a certain number of devices (e.g. 4 tape
drives). Second, there is Network Edition and Power Edition, where the
number of concurrently used devices is regulated.
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