[Networker] NetWorker oddity - is it me or just the way it works?
2008-10-08 10:35:07
This isn't really a question but more of an observation, really. I guess
I'd just like to hear what others have to say on this matter. I'm not
suggesting that this is news to anyone, but I really hadn't ever thought
about this before until I did some testing recently. I think this is
present in all NW versions, and it's simply the nature of the beast,
good or bad. No biggie, really, just want to make sure that I'm not
misunderstanding something.
OBSERVATION
By default, when NetWorker runs incrementals, it will back up any file
whose file status time has changed or is newer than the last time
incrementals ran. I know that that behavior can be changed to only use
mod time, via directives, but otherwise, it's file status time. And file
status time obviously includes more than just mod time changes like you
would expect when a file is modified or newly created. So, for example,
changes to the permissions, ownership, group, etc. would also force a
file status time change (ls -lc), even if reset to the same value. A
more subtle change, however, would be when moving a file from one
location to another, which also resets the file status time and thus
would force a backup. BUT, let's suppose someone renames a directory. In
this case, the directory's file status time (ls -lc) would change, BUT
the constituent files would still retain their previous times (not just
mod times, but file status times also). As a result, if an incremental
was run, only the pathname to the directory would be backed up and not
the files. I've tested this, and that's the case. Only a full, numeric
or running a manual incremental from the client, and specifying an older
date, will force those files to get backed up, unless of course you
affect a file status time change on them, e.g. 'chmod -R u+r dirname'.
So NW just sees the times and rather than noticing that the files are
now in different locations (different paths), it just ignores them since
they're not newer than the previous incremental.
PROBLEM
This seems like a potential gotcha because if a user renames a
directory, and then deletes the data, say a week later, and then you go
to recover the directory from that incremental then all you'd recover
would be the directory name. You'd have to go back further to get the
files, but how would you know where to find them since they were last
backed up under a different directory name??? Obviously, you could loop
through all the save sets (say over the last month) for the parent file
system using 'nsrinfo -s server -t nsavetime client' and grep for one of
the file names to determine which directory contained it, or you could
just browse around one day at a time, or some such thing, but it sounds
like the only real answer to this is to expect the user to provide more
info to clue you in as to the fact that the data had previously lived
under another directory?
Does this make any sense? Any comments?
Thanks.
George
--
George Sinclair
NOAA/NESDIS/National Oceanographic Data Center
SSMC3 E/OC3 Room 4145 | Voice: (301) 713-3284 x210
1315 East West Highway | Fax: (301) 713-3301
Silver Spring, MD 20910-3282 | Web Site: http://www.nodc.noaa.gov/
- Any opinions expressed in this message are NOT those of the US Govt. -
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