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Re: [Networker] How does NW backup data for single save sets?
2009-05-13 15:26:24
A Darren Dunham wrote:
On Wed, May 13, 2009 at 12:51:03PM -0400, George Sinclair wrote:
When NetWorker is backing up a *single* save set, does it send each file
over one at a time or does it wrap two or more files together into that
one stream?
Hmm. I'm not sure what the distinction is here.
Perhaps a better way to phrase my question is that if the content of
more than one file was ever being sent to the backup server at the same
time then is it the case that those would have to be from different save
sets (multiplexing)? Or is it possible that NW could somehow chose to
read the content of multiple files simultaneously (when only a single
save set is being backed up) and somehow wrap them together into one stream?
If I infer your response correctly, the answer is that only one file is
sent at a time when using a single save set. Tar doesn't have the
ability, however, to multiplex. I mean, you can only tar a single stream
to a tape at a time, but NW can interleave multiple streams (save sets),
but only one file at a time is being sent in each stream; any given
stream does not consist of multiple files wrapped together??
There's a single TCP stream that is receiving the serialized output of
'save'. Just like 'tar' serializes a filesystem. The data from one
file is independent within the stream, but there's still only one
stream. So I don't know if that's yes or no to your question.
Does it change its behavior from one save set to another, one client
to another, etc. or is it consistent?
I can't think of anything that would change this behavior for a normal
filesystem backup (rather than an application backup).
I'm assuming that one is using standard NW backups and not some
ancillary package that would enable block level backups. In other words,
when NW decides a file needs to be backed up, it backs up the entire
file - this is what happens in our case - and not just the low level
block changes.
Hmm. Both are true, but I'm not sure they're related. It backs up the
entire file, and each file is combined into a single stream of data.
--
George Sinclair
Voice: (301) 713-3284 x210
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