Re: [Networker] NetWorker oddity - is it me or just the way it works?
2008-10-08 12:00:46
This behavior has existed since at least NetWorker 5.x and it did get
us! I complained, but the best response I got from Legato was it has
been documented as a limitation in (I believe) the release notes of
all further releases of NetWorker. I guess EMC/Legato thinks users
that create millions of randomly named files by running their codes
should be able to remember the old pathnames to all those entries ...
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
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Roberta Gold
Lawrence Livermore National Laboratory
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