CINC question

[Doctorski]

Can someone explain to me why the following note appears in the sysadmin guide

Note NetBackup recommends that you do not combine differential incremental backups
and cumulative incremental backups within the same Windows policy when the
incremental backups are based on archive bit (default).

We are starting to take on various flavours of windows clients and I had planned to set up the policies in the same way as our *nix policies. ie FULL, CINC + DIFF in the same policy.

Not really a windows bod so some help would be appreciated. Our Windows bods cant shed any light on this !!

Many thanks - Darren

[Jason_Voyles]

This has more to do with how the OS and Netbackup manage the archive bit markings on the files when it backs them up. Windows and Unix have slightly different methods for determining what is needed to backup during an incremental. This is documented in the Windows Netbackup Administrators Guide I, page 343.
The problem occurs when a differential incremental kicks off before a cumulative incremental. The differential incremental will clear all of the archive bits (or timestamps for windows), When the cumulative kicks off, it will not see the bits (or time stamps) and won't backup the files. Therefore you will not have a true cumulative incremental.

It really is not a good idea to have a cumulative and differential incremental in the same policy that is scheduled to run concurrently at any time between Full's.

[Doctorski]

Many thanks Jason.

We never use the scheduler as all our backups are run via our job scheduler.

Bearing this in mind I think we are ok to have all 3 schedules in one policy as there is no chance they could run "out of sync"

[Yasuhisa_Ishika]

Think!

Schedule types are implemented as follows:

FULL: backup all files, and clear archive bit
CINC: backup files with archive bit, and never clear it
DIFF: backup files with archive bit, and clear it

Though if you run like "FULL, DIFF, DIFF, CINC", what happens?

...Yes, if you set retention correctly, no problem.
But you may be frightened by small CINC size. :p

[Doctorski]

Ok now I understand that we have a problem

[Doctorski]

Ok,
In the windows world what is the point of a cumulative incremental in that case.

You will not be able to recover from the last FULL and the last CINC and have all the changed files in between. (Unless as below DIFF retention is longgggg)

We planned to do .....

SAT1 - FULL (12 months retention) OFFSITE SET1
SUN1 - FULL (12 months retention) OFFSITE SET2
MON-FRI DIFF (14 days)
SAT2-4 CINC (1 month)
SUN2-4 CINC (1 month)

then round to SAT1 / SUN1 again

This is obviously wrong now I know how windows works !!

How then do you guys set up your windows backups.

Do you have long enough DIFFS to last between your FULLS ?

Why bother with a CINC ?

All backups are duped for offfsite.

Cheers - Darren (Happy with Unix, worried about windows ;-})

[Stumpr2]

> In the windows world what is the point of a cumulative incremental

Restore will only need the last full and the last cumulative images. Some people do weekly fulls and daily cumulatives which uses a little less resources than daily fulls.

with archive bit...Don't mix differential and cumulative in the same policy.Message was edited by:
Bob Stump

[Doctorski]

Cheers Bob, I kinda figured that out now !

Will look to change my windoze policies forthwith !

Guess its time to look at Synthetic CINCs on a non FULL weekend

[Yasuhisa_Ishika]

I preffer setting windows with incrementals based on timestamp.

[Doctorski]

Be careful with doing that.

Files/Directories copied from external sources may have a timestamp of BEFORE the last FULL. They therefore won't get backed up until the next FULL.

If you have a disaster before that FULL, they wont be on tape.

[Yasuhisa_Ishika]

Thank you for your telling me this issue! I'v never consider it.