From: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] On Behalf Of 
Jason Clarke
Last night, the client backed up 129GB, which is about 125GB more than
normal.

On any given day, during the holidays, theres about 2-3GB of changed
files.

However, I did change a permission on a directory/folder tree that
contains 125GB of files.

I'm guessing TSM has backed up the whole file because of the permission
change. I'm guessing this is because subfile backup isn't being used
here. If subfile was turned on for that client, would it reduce the
amount of data it decided to backup?

Yes, subfile backups would decrease the amount of data you would have backed 
up. However, you will eventually have to back up the entire set of files 
eventually, because subfile backups allow a limited number of deltas to be 
backed up, and will only affect files greater than 10kB and less than 2gB. Also 
keep in mind that if you have, say, 100,000 files, and you have 5 deltas for 
each file, you're going to have to make restore 600,000 locations on tape--1 
for the last full backup of a given file, and 5 for its subsequent deltas. 
Subfile restores are very, very slow, and are more designed to accommodate 
backups across slow (i.e., T-1) bandwidth pipes.

TSM treats files as whole entities. When you change permissions on a file, TSM 
will back it up again. Might I suggest that you stage such mass changes so that 
you don't get hit with such a spike again?

--
Mark Stapleton
System engineer, CDW

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