ADSM-L

Re: TSM vs Netbackup

2004-01-02 09:00:09
Subject: Re: TSM vs Netbackup
From: Andrew Raibeck <storman AT US.IBM DOT COM>
To: ADSM-L AT VM.MARIST DOT EDU
Date: Fri, 2 Jan 2004 06:59:43 -0700
I do not understand the blanket assertion that TSM does not have an online
snapshot technology. TSM does in fact have such technology, which is used
to perform online image backup (full and incremental) as well as open file
support during regular incremental backups. Some salient points:

- TSM's image backup function provides full and incremental backup
capability at the file system level. It does not yet support file-level
backup and restore.

- TSM 5.2.0's online image backup is supported on Windows 2003 on an "as
is" basis only; but it does exist. The 5.2.2 client now officially
supports snapshot technology on Windows 2003.

While the test clearly states that it uses TSM's default client settings,
in so doing, it is really making an apples-to-oranges comparison. While
TSM does not have snapshot technology for file-level backup, at the very
least the journal-based backup feature would substantially reduce
incremental backup run times once you're past the first backup.

Regards,

Andy

Andy Raibeck
IBM Software Group
Tivoli Storage Manager Client Development
Internal Notes e-mail: Andrew Raibeck/Tucson/IBM@IBMUS
Internet e-mail: storman AT us.ibm DOT com

The only dumb question is the one that goes unasked.
The command line is your friend.
"Good enough" is the enemy of excellence.




Richard Sims <rbs AT BU DOT EDU>
Sent by: "ADSM: Dist Stor Manager" <ADSM-L AT VM.MARIST DOT EDU>
01/02/2004 06:32
Please respond to "ADSM: Dist Stor Manager"

        To:     ADSM-L AT VM.MARIST DOT EDU
        cc:
        Subject:        Re: TSM vs Netbackup


>Veritas recently commishioned a "study" of performance between
>Netbackup, Networker, and TSM to compare results of snapshot backups.
>Apparently the new Netbackup 5.0 has a new "advanced client".
>For TSM, they threw it in stating that there is no comprable feature,
>but they wanted include it anyway.  I have never done any investigating
>into doing snapshot backups of data with TSM, do any of you do anything
>similar at your site and if so, what?
>
>Link to the marketing trash:
>http://veritest.com/clients/reports/veritas/veritas_backup_w_add.pdf
>
>Michael French
>Savvis Communications

Good morning, Michael -

Many of us don't much look at competing vendor offerings, so it was
interesting
to learn of the new Veritas FlashBackup approach.  I read through the test
report, and searched out the basal information at
http://www.veritas.com/van/products/nbuflashbackup.jsp
to get more information.  Some observations...

The VeriTest report is troublingly vague on just what Veritas contracted
them to
test.  The impression is left that VeriTest themselves determined just
what
would constitute the test environment.  We are given no information as to
what
their "large data set" is supposed to represent (active web server HTML
and
programs file system; user home directory file system; mixed database
environment; mail spools?).  Reading all the material, however, it is
apparent
that the test is to show the advantages of only FlashBackup within the
narrow
focus of backing up a large number of modest files (representative of user
home
directories, with their frequent file changes).

One thing that jumped out at me was that the test chose to use DLT tape
technology.  While DLT or LTO may be a relatively common deployment
choice, it's
well known that as principally streaming media that their performance
drawbacks
will prolong the backup of more than a million small files.  This will
inherently make any conventional file-oriented backup approach look bad in
the
test.

Almost comically absent from the test was the real reason that one
performs
backups: restoral.  We've all seen vendor literature touting one aspect of
a
product without presenting the overall whole view.  The FlashBackup
whitepaper
(unreferenced in the testing document) suggests that restoral time is
comparable
to the product's historical norm, but certainly one would like to see that
included in such a test.

I laud the innovative approach that Veritas has taken with FlashBackup:
it's
always good to see imagineering occurring in product development.  I'm
concerned
about the durability of this approach to file backups, though. FlashBackup
operates by first capturing a file system map (it has to run through the
file
system like other conventional products, and so can get somewhat bogged
down in
directories).  Then it separately writes disk blocks to tape, bypassing
file
system I/O overhead, whence it gains its speed.  This amounts to a kind of
file
system emulation.  Is this foolproof, particularly in highly volatile file
systems?  Will this work under all circumstances and all kinds of file
system
objects?  This is what we would have liked substantive, thorough testing
to tell
us.  We aren't getting that information from the vendor or their
contracted
testing company, so it will apparently have to be proved out in the field.

Some of the information surrounding FlashBackup can mislead.  The testing
paper
states that IBM's TSM "...does not have an online snapshot capability..."
Strictly speaking, that is true.  TSM does, however, provide image copy
backup
and restoral.  And there is the Tivoli Storage Manager for Hardware
product,
which takes advantage of the IBM ESS's Copy Services to facilitate DB2 and
Oracle backups.  This leads to the question of whether you want "flash"
type
backup capability in your backup product, or native to the file system
infrastructure.  Some file systems, such as AFS and DFS, are specifically
architected to support backups through a flash mechanism.  More hardware
is now
accommodating this need, particularly in 24x7 operations.

I would strongly advised reading FlashBackup's whitepaper, which gives a
much
more balanced sense of where FlashBackup offers advantages, and where it
does
not.  In particular, note that, in contrast to more generalized backup
products,
FlashBackup works only with certain file system types.  It would be most
helpful
to get some feedback from its beta testers.

  Richard Sims

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