In the below scenario, I have a NetApp filer that I am backing up the
/vol/widgets volume using image backups via Tivoli TSM NDMP. To keep the
scenario simple, assume the volume is associated with a Backup Copy Group
setting of:



Versions Data Exists: NOLIMIT

Versions Data Deleted: NOLIMIT (ignored for NAS image backups per TSM docs)

Retain Extra Versions: 3

Retain Only Version: 3 (ignored for NAS image backups per TSM docs)



On the first day I do a FULL image backup. Objects shows up in the TSM
database "BACKUPS" table as the ACTIVE version

On the 2nd day, I do a DIFF image backup. In the TSM Database "BACKUPS"
table, the DIFF image shows up as ACTIVE while the FULL image shows up as
INACTIVE.

On the 2nd day, during expiration processing, nothing is deleted (FULL image
backup is 1 day old)

On the 3rd day, I do a DIFF image backup. In the TSM Database "BACKUPS"
table, this DIFF image shows up as ACTIVE while the previous DIFF shows up
as INACTIVE

On the 3rd day, during expiration processing, nothing is deleted (FULL image
backup is 2 days old)

On the 4th day, I do a FULL image backup. In the TSM Database "BACKUPS"
table, this FULL image shows up as ACTIVE while the previous DIFF shows up
as INACTIVE

On the 4th day, during expiration processing, the 1st day FULL image backup
is deleted (it is 3 days old)





My questions are:



1: When you want to restore a NetApp volume to a state that existed between
FULL image backups, do you not have to restore the FULL image backup
associated with the DIFF you want to restore to, and then restore the DIFF,
and if not, why not?

2: Using the scenario above: If, on the 4th day, I wanted to restore my
NetApp to the state it was in on the 2nd day, would I not have to restore
the 1st day FULL and then the 2nd day DIFF? If so, does this mean that in
order to be able to restore to any DIFF in between FULLS, my RETAIN EXTRA
VERSIONS should always be set to (DESIRED RETAIN DAYS + no. of days between
FULLS) to ensure I always have the FULL image backup associated with all
DIFF image backups of that backup 'series'? For example: If I want the
ability to restore a DIFF up to 14 days after it was taken and I plan on
doing a FULL every 7 days, I would want my RETAIN EXTRA VERSIONS to be set
to 21. This will allow me to restore the 1st FULL + the last DIFF associated
with the 1st full up to 14 days after that last DIFF was taken. On the 22nd
day, the FULL would expire, making the DIFFs associated with that FULL
un-restorable/useless.



If this is the case, it seems like you have to balance your restorability
desires with storage capacity requirements - even more so than you do with
normal file-level backups.



3: Lastly, with 5.1 TSM server, it appears that you have the ability to do a
file-level restore of an NDMP NAS image backup, if you performed the backup
with a TOC. If so, how does this affect the above configuration? It seems
like this makes NetApp NAS image backups more file-level (like regular
LAN-client incremental backups) as opposed to block-level (this is assuming
that NDMP backups of NetApp volumes are block-level, which I am unsure of at
this point! :-) )



Rick Stratton