Re: progressive backup vs. full + incremental

All the replies are correct and they are the reasons why incremental
forever is better and need less time to restore. Maybe a real example can
help you. I had more than 8 years in operations and I can say that TSM is
much better. I had the following experience:

Some "great" application developer create files using date as a part of the
file name. Some of these files are vital e.g. price files, but some are
not important, e.g. temp working or log file for trace. The backup job
needs to backup all the files. The disk crash on Friday and we need to
restore the files.

For traditional FULL + INCREMENTAL, I need to restore all these date
specific files which are useless, so it is a waste of time to restore them.
The bad news did not stop here. I found out some of these date specific
files are huge ("smart" developer write everything to log file, so that
they are able to trace if there is problem). The application will delete
these files in a "day-end" job to reclaim the disk space. However, FULL +
INCREMENTAL will restore all these huge temp files. As a result, I ran out
of disk space when I restore the daily incremental. So I had to delete
those temp files, restore the second incremental, delete temp files,
restore the third incremental,... until incremental of Friday morning. The
total time to restore include this manual delete files process that people
often ignore and forget.

For TSM, it will not restore these intrim temp files and only restore the
files I need using point-in-time restore feature. FULL + INCREMENTAL is
not able to do. Therefore, it is much better.

Hope this example can help you to explain and understand why TSM is better.

Thanks & Regards
William

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Progressive incremental backs up only new or changed files. during the
initial backup the client backs up all eligible files of course(full
backup). Subsequently, files are backed up again only if they are new or
have changed since the last backup. In TSMs case, a pointer to each version
of every file for every client is kept in the database , so there is no
need for another full backup.
When you need to restore, you can choose the specific version of the file
or point-in-time to restore, and TSM will restore only that particular
file or files. The approach used for full + incremental backups (NetBackup)
requires an initial full backup, followed by regular incremental or
differential backups (usually once a day), with the complete cycle needing
a full backup to be repeated on a regular (usually weekly) basis. This
backup method results in redundant weekly full backups of files that have
not changed, wasting both network and media resources. The multi-step
restore process in this approach requires the software to restore the last
full backup, then to restore incremental or differential backups on top
of that in order to recover the latest version of a file or an entire
system. This methodology not only involves restoring more data, it also
means more tape mounts and tape positioning and consumes more network
bandwidth all of which amounts to having longer restore times.

Cordiali saluti
Gianluca Mariani
Tivoli TSM Global Response Team, Roma
Via Sciangai 53, Roma
phones : +39(0)659664598
+393351270554 (mobile)
gianluca_mariani AT it.ibm DOT com
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The Hitch Hiker's Guide to the Galaxy says of the Sirius Cybernetics
Corporation product that "it is very easy to be blinded to the essential
uselessness of them by the sense of achievement you get from getting them
to work at all. In other words ? and this is the rock solid principle on
which the whole of the Corporation's Galaxy-wide success is founded
-their fundamental design flaws are completely hidden by their
superficial design flaws"...

Joni Moyer
<joni.moyer@HIG
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Subject
progressive backup vs. full +
05/03/2003 incremental
15.21

Please respond
to "ADSM: Dist
Stor Manager"

Hello everyone!

I was wondering why the full + incremental would result in a longer restore
time than the progressive backup methodology? From several co-workers
point of view they thought that it would be quicker on the full +
incremental because you wouldn't have to go back to the beginning backups
of the file and restore all of the incrementals, you would just go back to
the most recent full backup and apply the incrementals after that point.
When I went to explain the reasoning behind this, I had some problems
understanding the concept myself, so I was hoping someone could explain
both methods and why they differ in restore time and why progressive is
better than the full + incremental. Thank you so much for any help you can
lend on this matter!

Joni Moyer
Systems Programmer
joni.moyer AT highmark DOT com
(717)975-8338