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Quibbles – Why can’t you clone or stage incomplete savesets?

Posted by Preston on 2009-10-27

NetWorker has an irritating quirk where it doesn’t allow you to clone or stage incomplete savesets. I can understand the rationale behind it – it’s not completely usable data, but that rationale is wrong.

If you don’t think this is the case, all you have to do to test is start a backup, cancel it mid-way through a saveset, then attempt to clone that saveset. Here’s an example:

[root@tara ~]# save -b Big -q -LL /usr
Oct 25 13:07:15 tara logger: NetWorker media: (waiting) Waiting for 1
writable volume(s) to backup pool 'Big' disk(s) or tape(s) on tara.pmdg.lab
<backup running, CTRL-C pressed>
(interrupted), exiting
[root@tara ~]# mminfo -q "volume=BIG995S3"
 volume        client       date      size   level  name
BIG995S3       tara.pmdg.lab 10/25/2009 175 MB manual /usr
[root@tara ~]# mminfo -q "volume=BIG995S3" -avot
 volume        client           date     time         size ssid      fl   lvl name
BIG995S3       tara.pmdg.lab 10/25/2009 01:07:15 PM 175 MB 14922466  ca manual /usr
[root@tara ~]# nsrclone -b Default -S 14922466
5876:nsrclone: skipping aborted save set 14922466
5813:nsrclone: no complete save sets to clone

Now, you may be wondering why I’m hung up on not being able to clone or stage this sort of data. The answer is simple: sometimes the only backup you have is a broken backup. You shouldn’t be punished for this!

Overall, NetWorker has a fairly glowing pedigree in terms of enforced data viability:

  • It doesn’t recycle savesets until all dependent savesets are also recyclable;
  • It’s damn aggressive at making sure you have current backups of the backup server’s bootstrap information;
  • If there’s any index issue it’ll end up forcing a full backup for savesets even if it’s backed them up before;
  • It won’t overwrite data on recovery unless you explicitly tell it to;
  • It lets you recover from incomplete savesets via scanner/uasm!

and so on.

So, logically, there makes little sense in refusing to clone/stage incomplete savesets.

There may be programmatic reasons why NetWorker doesn’t permit cloning/staging incomplete savesets, but these aren’t sufficient reasons. NetWorker’s pedigree of extreme focus on recoverability remains tarnished by this inability.

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2 Responses to “Quibbles – Why can’t you clone or stage incomplete savesets?”

  1. Brett said

    Another irritation (at least for me) is how one easily determines if a cloned saveset was successful? Or in other words, how do I easily get a list of all my aborted cloned savesets?
    If I clone a saveset and that clone fails, my copies attribute of the saveset is still incremented. Now if I purge my saveset off my VTL based on number of copies, since… hey copies is now two and I cloned to physical tape, I am going to be in trouble down the road.

    • Preston said

      Hi Brett,

      Keep an eye on the ‘validcopies’ feature in NetWorker 7.6 – I did a blog article about it recently (https://nsrd.wordpress.com/2009/12/04/validcopies-hazardous-sanity). While it’s still a little buggy in that it can sometimes report zero valid copies instead of the correct number, it does exist entirely for the purpose of reporting the actual number of recoverable copies of a saveset, as opposed to the total number of copies of a saveset.

      Cheers.

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