Veritas-bu

[Veritas-bu] Datacenter versus TSM

2003-03-12 11:19:28
Subject: [Veritas-bu] Datacenter versus TSM
From: david AT datastaff DOT com (David A. Chapa)
Date: Wed, 12 Mar 2003 10:19:28 -0600
Well Dan I did a comparative analysis of ADSM and NBU a few years ago for a
client.  I haven't looked at TSM much recently, but I remember from meetings
with IBM that they were going to make ADSM more like NetBackup with regards
to the scalability and master/media concept.  This may be completely wrong
with today's product, but this is what I remember from doing this work.

In the past ADSM (pre-TSM) had some very significant problems with scaling
after it was installed.

1.  Use of a proprietary Database meant that you had to pre-allocate disk
space to be used for your database, if you outgrew this space, it was not an
easy task to re-size
2.  Performance tests that were run in their NY facility claimed some very
large amount of data (~1TB) was backed up in a very small window (~1hr?).
Here's what the important thing to realize, they were able to achieve those
speeds because they had 16 individual ADSM servers backing up an ORACLE
database.  These 16 servers didn't know about each other and maintained
their own database, no single repository for meta data as with NBU.

The other things that I noted was their paradigm for backup was different,
Incremental forever.  Their spin is why should you back up the data over and
over again if you don't need to.  Good point, and I kind of like this
idea...however, when I added it all up I became increasingly more concerned
about database corruption and recoverability.  What if your backup database
had problems?  What was the course of action to restore/recover?  While I
liked the idea, it was too questionable for client/server technologies,
perhaps not as much in the mainframe world, which is where TSM/ADSM
originally came from (AD*Star).

Another issue I found to be quite bothersome, is this bit called
reclamation.  TSM has two modes of backup, co-location or non co-location.
Basically it will co-locate all data without regards to how long it will be
retained and non-co-locate doesn't.  Much like the NBU default behaviour for
not mixing retention levels.  However, I believe in the interest of
performance and time, co-location is recommended, which means there must be
another process somewhere that manages these mixed retention levels
otherwise you'll have "holes" on your tapes and very inefficient use of
expensive media.  So this is call reclamation.  This reclamation process
reclaims all of the space on the tape by moving the data with similar
retentions to like media.  Nice process, very cool, but if a reclamation
process is not finished yet, your backups cannot run, they must wait for the
reclamation process to finish before a backup can start.

Before they bought/integrated with Tivoli, there was no way to push out the
backup client you had to manually install it on each server.  With the
integration of Tivoli you can use NetCourier to carry the installation
package to the client and have it done that way.

I do not remember their interface, both gui and command line, to be easy.
There is a significant learning curve.

The client that had me do this analysis decided to go against my
recommendation to stay with NBU and went with TSM.  They spent lots of money
and have recently called me up to help them move back to NetBackup not more
than 18 months later.

Having said that...there are some very cool things about TSM.  The coolest
thing is that is caches backup to disk before streaming to tape...or should
I say SCREAM to tape.  This is something that I would love to see VERITAS
do, but I think I have an idea that will achieve the same thing without
having VERITAS' code being changed.

I hope some of this is helpful, as I mentioned before, please make sure you
validate anything I put in this email, since it may or may not have changed.

David

<><><><><><><><><><><><><><><><><><><><>
David A. Chapa
Backup Storage Consultant
DataStaff, Inc.
http://www.datastaff.com
312 683 1144
---------------------------------------

-----Original Message-----
From: veritas-bu-admin AT mailman.eng.auburn DOT edu
[mailto:veritas-bu-admin AT mailman.eng.auburn DOT edu]On Behalf Of Dan
Chrastil
Sent: Wednesday, March 12, 2003 9:35 AM
To: veritas-bu AT mailman.eng.auburn DOT edu
Subject: [Veritas-bu] Datacenter versus TSM


I have been using netbackup here for over 5 years and now my company is
thinking about going with one vendor for the entire
company nationwide.  Does anyone know where I may find a comparison between
netbackup and TSM.

thanks


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