Hi Jonathan,
On 27/11/2008, at 10:22 , JGillTech wrote:
Thanks again for the clarification. However, I am not solid on the
concept.
I looked through the NetWorker documentation for an explanation of
ssid vs. clone id. I didn't find anything that could help me
discern the difference.
I was under the impression the ssid was the unique identifier of the
save set. Can a ssid be reused? I was under the idea that each
save set specified in a client resource is assigned a unique ssid
when backing up. Correct me if I am wrong. If that is true, why is
a clone id needed?
The clone-id is used to differentiate _instances_ of a saveset.
If you have your "original" saveset on say, tape 800841, and a clone
on tape 800917, and you only want to affect _one_ instance of the
saveset, you have to be able to uniquely identify that instance. Thus,
that's where the clone-id is used.
Why would NetWorker pick a save set with the lowest clone id? It
makes sense to increment the clone id of the most recent rather than
decrement. To clarify my understanding, the most recent instance of
a save-set has a clone-id 1 less of the previous.
No, I may have confused you by using an example from disk backup units.
The clone-ids assigned to individual instances of a saveset will vary
considerably, based on the time that the saveset instance is generated
- this is where I was saying that the clone-id is closely related to
the nsavetime. The reason NetWorker assigns (on disk backup units) a
clone-id for the media database instance of the saveset on the read-
only portion that is 1 less than that on the RW portion is explicitly
to ensure that a recovery request will target the RO device, not the
RW device.
The reason NetWorker picks the saveset _instance_ with the lowest
clone id is a historical one - in a situation where you backed up to
tape, then cloned to another tape and sent that other tape off-site,
it needed a mechanism for determining which saveset it would request
in the event of a recovery. For whatever reason, the design choice was
made that it would request the lowest clone-id (or at least, over
time, this became the design).
For pure tape environments, this usually works.
I currently make my volumes as full and record the location when
taking a clone tape offsite. Should I use the offsite flag rather
than making the volume as full? How do you apply the offsite flag?
I don't know of any place to do this within the GUI. I wish this
kind of stuff was documented. I have all the recent documentation,
I wasn't able to find any of this information.
Marking the volume as offsite has nothing to do with marking the
volume as full.
There is currently limited access to the media database flag
associated with offsite; it can't be (to my knowledge - I haven't
looked lately) controlled via the GUI. From the command line, you can
do:
nsrmm -o offsite volumeName
or
nsrmm -o notoffsite volumeName
However, you can't _query_ this flag.
Do you have anything more to say about clone-ids to help me
understand... specially the difference between clone-id and ssid.
Perhaps all I can add is that if you're not currently cloning your
data, the concept of clone-id fields may not seem all that logical.
However, when you're at a point where you have multiple instances of a
particular saveset, you do need a way of differentiating those
instances.
Cheers,
Preston.
--
Preston de Guise
"Enterprise Systems Backup and Recovery: A Corporate Insurance Policy":
http://www.amazon.com/Enterprise-Systems-Backup-Recovery-Corporate/dp/1420076396
http://www.enterprisesystemsbackup.com
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