ADSM-L

Re: [ADSM-L] How to Incorporate a CDL into TSM environment?

2007-06-08 02:34:38
Subject: Re: [ADSM-L] How to Incorporate a CDL into TSM environment?
From: Curtis Preston <cpreston AT GLASSHOUSE DOT COM>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Fri, 8 Jun 2007 02:32:49 -0400
Josef Weingand said:

>why do you want to use a VTL with TSM? 

I get this question a lot in my talks.  The first thing I'd say is for
the same reasons we want to do it in other environments: performance and
manageability.  Backups and restores rock with a VTL and that's all
there is to it.  Second, the manageability of a GOOD large VTL vs many
smaller disk pools in a large environment is significantly different.
If you have a good VTL that can scale to meet your needs, you get to
manage one device.

>Do you want to replace with a VTL your physical tape, or do you want to
>replace the TSM disk pool?

If you read my other response to John's post, you'll see that my opinion
on this is the former.  I still think you need a disk pool of some size
(e.g. one day's backups) to reduce tape mount contention.  But I think
it can replace that part of your tape library that's meant to store all
on-site tapes.

>Or do you want to have more LAN-free backup?

Not an "or," but an "and."  If I don't want to, I don't have to worry
about tape drive sharing, or purchase 3rd party products (i.e. Gresham)
to share a tape library (you have to do that to share an ACSLS tape
library between multiple LAN-free clients).  A VTL allows me to give
every large server that needs a tape library its OWN tape library if
that's what I want to do.

>Replacing the disk pool, you  might just get the advantage of
compression,
>however, compression with VTL you always need to consider the
performance
>impacts with compression enabled.

Most VTLs are using hardware compression now just like your tape drive.
If you're using NAS as your disk storage pool, another thing you may
consider is Storewiz.  It does compression of data going to NAS mounts,
and it does it inline just like tape compression, actually improving
performance not hurting it.

>Replacing physical tape, leads to more pwr (and cooling) cost. A 200 TB
VTL
>needs about 280 000 Euro/U$ more (for pwr and cooling) over a 6 years
time
>frame compared to tape. Ok, some countries on the world does not care
about
>pwr and green house gas (yet).

Hey, I think that was aimed at us. ;)  First I can tell you our contry's
position on that matter is likely to change drastically in about 18
months.  Second, I can tell you that it's a bigger problem over here
than you think for datacenters.  The problem is that in many places, you
actually can't get more power.  If you need more power, you have to buy
somebody else's building and take their power -- no kidding.  Finally,
I'll tell you that the concept of green storage is one of the hottest
topics at the conferences I've been attending lately.

Now, on to your comment.  I'd say it's true w/o de-dupe.  However, if
I'm storing multiple versions on a de-dupe VTL and it reduces the data
by 20:1 (or anything near that), the amount of power it consumes changes
drastically.  Another thing is that disk drives, while they usually spin
all day long (although not in all VTLS: see copansys.com), they are much
more power efficient than tape drives.  Then consider how many hours in
a day tape drives spin in a typical TSM environment.  I'd wager that a
de-dupe VTL spinning disk all day would consume less energy than a
similarly sized tape library running anywhere near 24x7.  I've actually
seen a case study where this was done and the de-dupe vendor won.

>thinking about100 - 200 session in parallel, you are not able to handle
100 >- 200 tape drives on your TSM server. Therefore, in my eyes, a VTL
will not >replace a prim disk pool in a medium to large TSM environment.

Copycat. ;)

>Using the IBM Tape Device Driver is only allowed for IBM tape products.
>It is illegal to use EMC CDL with the IBM Tape Device Driver!!! Only
the
>IBM VTL TS7510 and TS7520 are using the IBM Tape Device Driver.

Illegal is a strong word.  Do you mean unsupported?  That falls into the
"gimme a break" category for me.  Especially since the software inside
the TS7510 is the same exact software as what's inside the EMC CDL.  If
it works for the 7510, it's going to work for the CDL.  I have, however,
been in some shops where they not do something that was obviously a Good
Idea just because their vendor said "we won't support that
configuration."  

I'm too much of a "customer is always right" type.  If I were put in
that situation by IBM, I would mention that that this appears to make
their position as a combo software/tape hardware/disk hardware/OS
platform provider a liability instead of an asset.  Perhaps I should go
to a vendor that won't hold things over my head like that.

I've used this same tactic with Symantec when the force customers to use
their volume manager or explain how they don't like to work with EMC
products since EMC bought NetWorker.  I've used it with EMC when they
tell me they come out with a cool new feature on a DMX/Symmetrix that's
only usable if I use their backup product.

>this is a general sizing question. In a well designed/sized TSM
>environment, there should no prbl with reclamation

agreed