IBM Rescue & Recovery Incremental Backups

[Leon]

I use IBM R&R for "local" backups, so if I have an emergency on the road (hasn't happened yet), I can restore. I also, of course, do "off machine" backups. My question is regarding the R&R Incremental backups. How reliable is the IBM R&R Incremental implementation. I.E., can I rely on R&R to restore my system reliably to where it was on the date of my last incremental backup. Or, is it safer/better to always do Full/Base backups. Has anyone restored from the increments and had good results?

[egibbs]

Can't answer your question but I'd like to expand it a bit - how exactly are the incrementals calculated? Is it the differential from the base to the current point, or from the last incremental to the current point? And if the latter, does it actually look at the last incremental in the backup location or does it just remember the last time you did an incremental?

The reason I ask is you are only allowed 5 incrmentals at a time. Suppose I copy the base and all 5 incrementals off to DVD, and then delete only the incrementals, leaving just the base. If I go to do a new incremental will it then capture all differences btween the orignal base and the current state, or will it only capture the changes since the last incremental?

Ed Gibbs

[Leon]

You've done a good job of elaborating on my question....the answer to this will be useful for all who may be using this important utility under incorrect assumptions.

[s0larian]

@Leon:
I never had problems with restoring from incrementel backups. There is no need to do always a full backup.

@egibbs:
The incremental backup archive the files that have changed since the last incremental backup was taken. When the sixth incremental backup is taken, Rescue and Recovery combines the two oldest incremental backups (i.e if there are two versions of a file, just the newest one is taken of the two oldest incremental backups). The MaxNumberOfIncrementalBackups can be set in the file TVT.txt up to 32 (the file is located at c:\program files\IBM\IBM Rapid Restore Ultra). If you delete all incremental backups leaving just the base backup, the next incremental backup will capture the difference between the base backup and current state.

[egibbs]

Thanks for the info s0larian - especially the bit about changing the number of incrementals. I backup to NAS so space is not an issue - I hated being limited to 5 incrementals and was sure there must be a way to increase it, now I know.

Interestingly the bit about "Rescue and Recovery combines the two oldest incremental backups" doesn't work for me. If I already have 5 incrementals and try to make a sixth it will run for 15 or 20 minutes, then fail and say the backup could not be completed. It's probably because of my backup device - it's running a custom embedded Linux and R&R is probably trying to use some Windows proprietary APIs or something to combine the files on the device.

It's good to know that if I delete all the incremental R&R will be smart enough to capture the Base -> Current differential. So now I won't have to keep re-creating the Base every time I clean off the incrementals.

Thanks again,

Ed Gibbs