is there a reason why a full,Differential Incremental and Cumulative incremental should backup same amount of data ?

[nbuno]

Guys,

let me start with saying that i know what a full backup,Diff inc & Cum inc backup means. "theoritically"

when i tried to prove that by creating a folder "test" with 10 filles in it and tried running a diffrential backup after a full backup (note that no file changes took place in between,so that i can prove that no backup should get backup) it backed up again data as much as FULL backup !! i.e all the 10 files.

also,when i tried a cumulative backup it picked up the same data too !

any ideas ??

THANKS 

[mph999]

Yes, after the full backup, wait 10 minutes and 1 second, then run the incremental ...

Martin

[Marianne]

Please ensure that Full and Incr schedules are in the SAME policy.

If schedules are in different policies, they will be evaluated independently - Incr will be treated as if no backup has been done before.

[nbuno]

Marianne--> yes i did make sure that schedules are in same policy so that doesn't seems to be an issue

mph999--> is there a specific reason about you saying keeping a time gap between running of backups.i am just curious :)

[mph999]

Yes ...

"For incremental backups, NetBackup determines the time that has transpired since the last FULL backup and the current backup. This is the 'Delta Time' and is passed to bpbkar binary with the '-dt' argument. This value is used by incremental backups to determine if files or directories have changed. This time is combined with the TIME_OVERLAP variable that is specified in the client host properties to provided the 'Calculated Delta Time' used to determine objects to be backed up.

It's a bit confusing, but certainly, you used to have to wait 10 mins ... it may have changed at 7.x, never tested it, but for the sake of waiting 10 mins, let's try it.

Thanks,

Martin

[nbuno]

or so ..i want to go more deep into this to understand it..or if you could yourself can post few more crucial poinths here..like what exactly is TIME_OVERLAP variable and how it works..

also,does this mean that the bigger the data the more delta would be there,since NBU will take more time to back it up and this way it will get more time to evaluate things by its own..in other words..if backup data is such that it will be taking more than 10 minutes to get backedup its fine..but if data is so low that it will get backedup within 10 minutes and next backup will run before 10 min then that would again be picked up as FULL backup ?

[mph999]

Lets see if it is relevant first.  Can you run a full, wait 11 mins then run an incr ...

M

[Yasuhisa_Ishika]

In timestamp based incremental backup, files to be backed up are determined comparing with date and time of previous backup. Time Overlap and secret 10 minuts(I used to say 5 minutes,does this changed?)affect as offset to this comparision to prevent files be not backed up by system time gap.

Backup time of each backup is the time when it bacpme runnin, and elapsed time of backup does not affect to incrementals. Don't mind.

[Yasuhisa_Ishika]

It is possible that; * all the files in backup selection have future modification date * incremental level of NDMP backup reaches 9 * read only volume with archive bit based incremtals

[nbuno]

there is no issue with a unix client..irrespective of the time gap (even after 10 sec !) if i run a inc after a full backup it will not pick any data..which is correct.

secondly,when i run backup of another folder (with slightly bigger size ) the inc backup is working fine..i.e not picking up all data like full backup.

@Yasuhisa->i am sorry but i don't think i followed u quite well on ur " other scenario" post..

[nbuno]

i tried running inc backup after atleast half and hour of full but still it is backing up as much data as a full backup do..what say ?

[AlanTLR]

nbuno,

   Can you please post the output of 'bppllist <policyname> -U', where policyname is the name of the policy you're using to back up?

bppllist is located in /usr/openv/netbackup/bin/admincmd/bppllist or C:\Program Files\VERITAS\NetBackup\bin\admincmd\bppllist

Also, from the root folder (C:\ or / (unix)):

/usr/openv/netbackup/bin/bplist -B -C hshspm07 -k <policyname> -I -PI -S wayback -R -t 13 -b -l -s 05/15/2012 -e 05/15/2012 "*"

or C:\Program Files\VERITAS\NetBackup\bin\bplist -B -C hshspm07 -k Windows-ASH-HSP-2 -I -PI -S wayback -R -t 13 -b -l -s 05/15/2012 -e 05/15/2012 "*"

[Yasuhisa_Ishika]

Hmm, I suppose that this was caused by Time Overlap setting on Windows clients which is set to 60 minutes by default.
Please try changing Time Overlap to 0, and run incrementals after 5 or 10 minutes.

[watsons]

This may sound silly.. but did you check and confirm your "incr" & "cinc" schedule names are not actually set to be "Full schedule"?

Is it just a Filesystem backup? 

Yasuhisa's "other scenario" also worth taking a look.

[mph999]

Time over lap set in the registry in windows I believe ...

[mph999]

Time over lap set in the registry in windows I believe ...

[Marianne]

Can we confirm that these tests are actually for a Windows client?

there is no issue with a unix client..

Can you tell us if Incrementals are based on Archive Bit (default) or based on Timestamp?

If Archive Bit, can you confirm that Archive Bit was cleared after the full backup?

Have you tried Incr based on Timestamp?

[nbuno]

thanks guys..overwhelmed by the response..infact i was expecting such surge of answers (after all ur guru's and this was challenging the way we know NBU works..right ?)

let me clear one by one and apologies if soemthing remains..i will do that ASAP.

Yasuhisa-->i read something about the time overlap setting..i am not sure but does it only works in case of time based inc backups ? i tried using archive bit method but that too didn't work in my case as read in the tech note of symantec.Can you explain a bit more pls..

watsons--> sometime i do silly mistakes but i assure you this time i m not..Inc schedule strictly mean inc backup..i confirmed that thousand of times..also,its just a filesystem backup..rather of few test files/folders.

Marianne-->My Incrementals are archive types.

Yes,i checked archive bit was cleared after backup

i haven't tried timestamp based backup yet.