All,

>> You can create the empty file /nsr/debug/striped_recover  which will mount
>> position and then read several tapes at once during your recover.
>>
>> Two limitations I found to this (Networker 6.1.2):
>>
>> a. If your recover spans more tapes than the number of drives you have it
>> won't work..it wants to load and position all the tapes before starting the
>> recover.
>>
>> b. Support from Legato is nil for this type of recover.
>>
>> That said,  some people running version 7 may be able to confirm that it,
>> indeed, does this type of recover??
>
> It is very good to know ! Also judging other posts I previously read
> regarding the restoration speed it looks like this became a default
> behavior in version 7 ? People say the restorations are a way faster in
> the new version. Can somebody confirm that Networker 7 uses multiple
> tapes during the restoration ?

I'm not exactly sure what this new behaviour is, but NSR 7 (out of the
box) does not seem to behave any different to other versions in this
respect.  If you do a large recovery (one that will cover multiple
volume) it still loads and reads them one after the other.  It makes no
attempt to pre-load the next volume that it knows it will need.

Having said that, NSR 7 is much better than previous versions at moving
a session from one device to another, both on backup and recover.
Older versions have each session dedicated to a particular device; if
another device is better for some reason (like it already has a
required volume mounted on it), tough (in this case it unmounts the
volume from that device and remounts it).

My impression is that the implementation of this is a kludge (the
sessions still seem to be tied to the one nsrmmd, but that nsrmmd can
now attach itself to a different device) so I'd expect to see some
limitations.  Implemented properly (say where the client could
reconnect to a different nsrmmd part way through a session) this could
be great.

The down side is that parallel recovers are now broken.  In the later
versions of NSR 5, if you run two recovers at the same time that both
try to read from the same volume, it does them both at the same
time as you would expect.  It even back-spaces the volume if the
second recover requires something that is before the current
position.  In NSR 6 and NSR 7 the two recovers seem to run sequentially;
the second one waiting for the first to finish with the volume.

George.
--
George Scott           George.Scott AT its.monash DOT edu
Systems Programmer, IT Services, Monash University

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