To preserve restore times from multiplexed tapes
NetWorker will read every chunk in a single pass. This
is by design of OTF. For example: if I need to restore
multiple files each from a different saveset on the
same tape it will grab all in a single pass rather
than do a rewind each time a new file needs to be
read. This certainly does lend itself to the behavior
you have seen in your testing, which is exactly the
reason there is specific saveset cloning, but also
dramatically enhances single file restores. Group
cloning inherits the single pass read as well.
To gain the demux you are looking for you will require
to do cloning at the savset level just as Curtis has
clearly represented.
I just wanted to ensure you realize that there is a
method to this madness.
-Steve
--- Curtis Preston <cpreston AT GLASSHOUSE DOT COM> wrote:
> I just sent a separate message with the subject "How
> NW cloning &
> multiplexing REALLY works." It contains the results
> of my tests that
> show how NW really deals with cloning and
> multiplexing. SUMMARY: At
> least in 7.3, it always preserves multiplexing
> unless you force it not
> to do so by specifying one saveset at a time via the
> GUI or nsrclone.
> This includes group cloning/automatic cloning,
> saveset cloning via the
> GUI or the command line, or volume cloning.
>
> ---
> 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
> ingo AT visionet DOT de
> Sent: Friday, January 19, 2007 7:18 AM
> To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
> Subject: Re: [Networker] Does cloning unmuliplex and
> make recovery
> faster?
>
> We are sometimes doing an
> 'mminfo -q <tell me what I want> -r ssid | nsrclone
> -f <pool> -S -f -'
>
>
> By the way, I always believed, cloning *would
> always* demultiplex; we
> usualy
> do automatic cloning after savegroup finish, and
> sometimes during
> cloning
> you can see the source tape wind forward (presumably
> searching the next
> records of *the* saveset being cloned at that
> moment) and backward
> (presumably after having finished cloning one
> saveset and picking up the
> next saveset on the worklist). Once I have some time
> left, I will have a
> closer look at the file and record positions.
>
> Ingo
>
>
> On Fri, 19 Jan 2007 09:58:46 -0500, George Sinclair
> <George.Sinclair AT NOAA DOT GOV> wrote:
>
> >rader AT GINSENG.HEP.WISC DOT EDU wrote:
> >
> >> > > I find it hard to believe that cloning
> preserves multiplexing,
> it's my
> >> > > understanding that nsrclone goes one by one,
> SSID to the next
> SSID
> >> > > cloning each singly before moving on to the
> next
> >>
> >> > It doesn't need to do that (at least not in the
> situations I've
> used
> >> > it), and it's very easy to test.
> >> >
> >> > Instead of copying one ssid at a time, it can
> maintain a list of
> ssids.
> >> > As it streams a source volume, data from any
> matching ssid is
> copied to
> >> > a destination volume. This has the big benefit
> of requiring only a
> >> > single pass on a source volume.
> >>
> >>And so for many years we've been semi-manually
> doing something like...
> >>
> >> BEGIN='05Jan07 2359'; END='06Jan07 2359'
> >>
>
QUERY="'!incomplete,level=full,'savetime>$BEGIN,savetime<$END"
> >> mminfo -r ssid -q "$QUERY" > ssidlist
> >> nsrclose -S `cat ssidlist`
> >>
> >>Is there a better way these days?
> >>
> >>
> >>
> >How about just nsrclose -b pool -S -f ssidlist
> >
> >>steve
> >>- - -
> >>systems & network manager
> >>high energy physics
> >>university of wisconsin
> >>
> >>To sign off this list, send email to
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http://listserv.temple.edu/cgi-bin/wa?RSS&L=NETWORKER
> >>
> >>
> >>
> >
> >
> >--
> >George Sinclair - NOAA/NESDIS/National
> Oceanographic Data Center
> >SSMC3 4th Floor Rm 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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