Nick,
I have several customers using de-dup appliances, including DD, and I think
they are all "happier" using NFS/CIFS type mounts than using VTL's, just
because functionally it's so much easier to manage that way.
With NFS/CIFS mounts, you just create a filepool, define the volumes, and off
you go, you'll have it in production in less than 8 hours. The only issues you
have to deal with are working out any timeout settings (especially on CIFS),
which is usually a one-time deal.
With a VTL setup, you have to deal with SAN zoning and create (and manage) the
TSM library-to-drive-to-OSaddress mappings, which some customers can't manage
on their own to start with, and doing 100 of them isn't fun.
Performance-wise, with NFS you are looking at the difference between managing
n-way IP connections and the throughput you get with that in your particular
network environment, vs. managing fibre connections to the VTL and the
throughput you get with that in your particular SAN environment, vs the
internal throughput of the device.
If you only ever do small restores, and an NFS mount through a standard GiGE
connection is all the throughput you need, almost any device on the market will
do that just fine (and I have some customers like that). If you are dealing
with backups of multiple multi-TB data bases, that's a whole different kettle
of fish performance-wise (and I have some customers like that, too). OTOH, if
you aren't doing LAN-free, your restore times are limited by the NIC connection
to the client, not the appliance, etc., etc., etc.
I know this answer isn't specific to the DD, which is what you are looking for,
but in every customer I have looked at, it was a question of matching the
capabilities of the specific appliance they were considering to the specific
requirements of the customer's environment. And no 2 appliances, or 2 models
of the same appliance, have exactly the same capabilities.
Things to watch for:
-Be sure to check the specs on the device you are considering (from any vendor)
to make sure its own throughput rates meet your needs (especially the SINGLE
I/O STREAM throughput rate).
-Are you comfortable with the vendor's stated response times for support?
(software or hardware). Ask for references of customers in YOUR support
district - I've found that service quality from some vendors varies wildly from
region to region.
-If at all possible, put your throughput (and reliability and service)
requirements in writing and have the vendor respond in writing that the device
meets those requirements.
And of course, the need for LAN-free trumps everything, no choice but VTL there.
Wanda
-----Original Message-----
From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of
Nick Laflamme
Sent: Tuesday, November 15, 2011 6:45 AM
To: ADSM-L AT VM.MARIST DOT EDU
Subject: [ADSM-L] Tape or NFS? (DataDomain specifically)
We've been told by consultants (these particular consultants shouldn't throw
stones) that DataDomain customers running TSM are far happier running NFS than
VTL, because DDRs are built primarily as file servers and the VTL function is
an add-on.
I can see the financial motive for staying with NFS (those VTL licenses aren't
cheap!), but I'm skeptical about the implication that there's a functional or
performance advantage to using NFS over VTL for a TSM server, in our case on
AIX.
Would anyone who's run both or chosen NFS care to comment? How much does it
depend on your infrastructure or your needs for LAN-free?
Thanks,
Nick
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