AW: [ADSM-L] Does subfile backup reduce tape occupancy?

I just started to use subfile backup and here are my observations:

* it saves a lot of disk/tape space *IF* used correctly
* you should use it for big files that don't change were much - we use it for 
Outlook PST files
* Don't use it for a complete file server -  the 1GB limit of the subfilecache 
will be reached immediately
(I've reached this limit by miscoding the include.subfile statement)
* Be aware of the "disadvantages" - detecting the changed blocks needs time and 
cpu. Restore will take
a bit longer to recreate the original file.

HTH
Thomas


-----Ursprüngliche Nachricht-----
Von: ADSM: Dist Stor Manager [mailto:ADSM-L AT VM.MARIST DOT EDU] Im Auftrag 
von Tab Trepagnier
Gesendet: Freitag, 04. November 2005 15:55
An: ADSM-L AT VM.MARIST DOT EDU
Betreff: [ADSM-L] Does subfile backup reduce tape occupancy?


Like lots of users, our tape libraries are overloaded and we're looking
for ways to reduce what we're keeping before spending money on new
equipment.

Server: TSM 5.1.10 on AIX 5.2
Clients: mostly TSM 5.1.7 on Windows XP/200x.
Storage: mix of disk, 3570, and LTO
Most filesystems are configured to maintain three versions.

If I have a server whose current occupancy is 1000 GB, and I turn on
subfile backups with the same number of versions, will the actual
occupancy go down?  Or will it remain the same?

Thanks.

Tab Trepagnier
TSM Administrator
Laitram, L.L.C.