There are three possible scenarios of cloned data. Which one of these
scenarios happens to you will be based on how you clone:
1. A group of SSIDs that were mpx'd get completely de-mpx'd when they
get cloned.
2. A group of SSIDs that were mpx'd stay mpx'd exactly the same when
they're cloned.
3. A group of SSIDs that were mpx'd are partially de-mpx'd when they're
the cloned.
Remember that ALL cloning is saveset cloning, whether you're doing
volume cloning (nsrclone -V <volume>), saveset cloning (nsrclone -S
<SSID>), or automatic cloning (group level cloning). In every scenario,
nsrclone is given a list of one or more SSIDs to clone. The only thing
that determines whether or not something is de-multiplexed is how
nsrclone was given the SSIDs. Consider the following scenarios:
1. Group level cloning. Nsrclone is given a list of SSIDs from the
backup that was just created.
2. Saveset cloning where nsrclone is given the name of a file with all
the SSIDs to clone.
3. Saveset cloning where nsrclone is given a list of SSIDs on the
command line.
4. Volume cloning where nsrclone is given the name of a volume to clone.
5. Saveset cloning where nsrclone is given only one SSID to clone.
Assume the following for the moment:
1. No SSIDs span tapes.
2. No other SSIDs are interleaved in with the SSIDs we want to clone.
(e.g. no other backups were running at the same time from another group
that we're not going to clone)
When scenario 1, 2, 3, or 4, nsrclone is given a list of SSIDs, and it
clones them all, with mpx intact, and the cloned volume(s) will look
exactly like the original volume(s). You can verify this by looking at
the offsets of the savesets on the tape.
When scenario 5 happens, however, it will de-mpx the tape, as it's only
cloning one SSID.
Now, consider these additional scenarios:
Scenario 1, 2 or 3 above where the list of SSIDs were interleaved with
other SSIDs. When this happens, obviously it's going to de-mpx a little
bit, as you're not cloning all the same data. But it's not going to
completely de-mpx the data. It's just not going to be mpx'd the same
way the original was.
Scenario 4 where some SSIDs span that volume and go onto another volume.
When this happens, the SSIDs that reside entirely on the volume will be
mpx'd exactly the same. However, when it starts cloning SSIDs that
spanned to another volume, where or not they get somewhat de-mpxed will
be based on whether or not they were mpxed with other SSIDs that are not
getting cloned.
---
W. Curtis Preston
Author of O'Reilly's Backup & Recovery and Using SANs and NAS
VP Data Protection
GlassHouse Technologies
-----Original Message-----
From: networker-bounces AT backupcentral DOT com
[mailto:networker-bounces AT backupcentral DOT com] On Behalf Of Fazil Saiyed
Sent: Wednesday, January 17, 2007 5:56 AM
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Subject: [Networker] Does cloning unmuliplex and make recovery faster?
There would have been easy way to find that out.
Just look at original volumes and the savesets on them, then compare
with
cloned tapes, you will have your answer, however, other post have
indicated that there in no difference in cloning results wheather auto
or
manual that it DOES Demultiplex. ( baring small saveset belew 100 mb).
Either way, backing up to Disk and staging may be the cleanest and
fastest
way to clone.
Thanks
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