Networker

Re: [Networker] 2 Part Question

2007-05-15 13:04:20
Subject: Re: [Networker] 2 Part Question
From: George Sinclair <George.Sinclair AT NOAA DOT GOV>
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Date: Tue, 15 May 2007 12:59:16 -0400
Darren Dunham wrote:
Can someone explain the cloning process to me as to why it would be
more efficient to do a restore from a clone pool tape, and why this
would be a good idea to use the cloned tapes at a disaster recovery
test site to speed up things?

If you clone on a saveset-by-saveset basis, you demultiplex that
saveset and create a single chunk of data to read, leading to improved
restore performance (think of it as defragmenting your tape backups).
However, there's been recent discussion on this list which suggests
that there are ways in which the clone backup isn't demultiplexed, in
which case there would be little benefit apart from redundancy and
confirmed reliability.
Non-demultiplexed cloning happens if you pass multiple savesets into
nsrclone (instead of running them one at a time), and the savesets are
relatively multiplexed.  Demultiplexing the savesets takes more time
than straight cloning, so the time requirements may not allow you to do
that.

Not to re-open that can of worms, but did we ever conclude what happens when cloning is enabled for a group? I want to say that that's tantamount to passing multiple savesets
into nsrclone?

George

--
George Sinclair - NOAA/NESDIS/National Oceanographic Data Center
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