Note that the responses below assume you're running VSM for Unix.

kmcdonal AT ds13.argv DOT net writes:
> 
> 
> I have a couple of questions about how netbackup handles filesystems
> with storage migrator:
> 
> 1.  Does netbackup use ctime or mtime in the inode to determine if the file
>      needs to be backed up in a differential incremental?

mtime.  But with VSM it will also depend if the configured number of
VSM copies have been made (and are in an 'active' state) - in which
case only the inode is backed up.

> 
> 2.  If I have a file that has been migrated to tape, is purged from disk, and
>      is cached back to disk such that it shows as being 'cached' by the migloc
>      command in VSM, is that file skipped during backups with NBU?  Or does it
>      have to go back through the 'premigration' again and get marked as 
> migrated
>      to be skipped by NBU?  It should skip it since the file has valid VSM 
> tape
>      copies of the data, but I'm not sure it does skip it.
> 

If the file is unmodified, the tape copies will still be 'valid'
(e.g. show up in mogloc).  If the file is changed, the tape copies
will become obsolete, and the entire file will get backed up (assuming
the file is not remigrated first).

> Thanks,
> 
> 
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-- 
Larry Kingery 
                         This space for rent