Networker

Re: [Networker] Group wants to run a full?

2010-02-28 16:37:38
Subject: Re: [Networker] Group wants to run a full?
From: George Sinclair <George.Sinclair AT NOAA DOT GOV>
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Date: Sun, 28 Feb 2010 16:36:07 -0500
Davina Treiber wrote:
George Sinclair wrote:
I have a tape pool that I turned off indexing on (Store index entries=No). Also, selected the 'No index save' option for the group. I then ran a full on the group. It completed just dandy. I then ran an incremental estimate on the backup server as:

savegrp -n -l incr group

and it reports that no full backups of this save set were found in the mediadatabase; performing a full backup. However, I can query the media database, and it reports the save set (no spelling mistakes).

Isn't an incremental based on the last media database entry, not the CFI? Something seems odd here:


Think about this a minute George.
Running an incremental requires that the server knows the details of each file that was backed up in the full, thus you MUST have a CFI available. If you turn off indexing you simply cannot do incrementals or level backups.

Well, I thought that the CFI was only used for recovers and that NW based its backup criteria on change of file status time (default) for the file, as in if it's change of file status time is more recent than the last time its save set (parent save set; e.g. /var for /var/file.txt) was backed up then it gets backed up; otherwise not. The date/time for the parent save set is contained in the media database, right? So if something as simple as the group, owner or even file permissions change, as opposed to content (mod time), then the file status time (inode info) changes, not mod time, but in either case, it could determine that it's more recent than the last time the related save set was backed up by checking the media database?
clearly, there must be a flaw in my thinking, though?


Why would you do this anyway? You might save a miniscule amount of disk space but disk is cheap these days. The saving is hardly worth it when you consider the cost to your employer of your time to micro-manage this. If I was you I would just turn the indexing back on and stop worrying about it.

This was just a test using a test pool. But this brings up a question, which I've outline below. The reason I wanted to exclude all indexing is because I plan to recycle this tape. If I do that, what happens if other 'legitimate' backups for this client (e.g. other NSR client resources/groups for this client) are also backing up this same save set? Once I remove the volume, what if there was a later incremental back up of that same saveset from some other pool, client resource? How could I recover the whole thing since it based its incremental on the one before and the one before that ... all the way back to the previous full. If you remove one somewhere in between then how could you rebuild the whole thing? Keeping it non-indexed seemed like a good way to avoid compromising the other backups of this save set? Not sure if I'm explaining it correctly, but maybe my understanding here is wrong?

Let's say I have two NSR client resources for ralph, both members of two different groups, each a member of two separate pools. Both clients have the following save set:

ralph:/home/junk

Let's suppose the backups go like this:

ralph (1 of 2) level full vol TP1
ralph (1 of 2) level incr vol TP1
ralph (1 of 2) level incr vol TP1
ralph (2 of 2) level full vol TP2
ralph (2 of 2) level incr vol TP2
ralph (1 of 2) level incr vol TP1

If I remove volume TP2, I loose all the media database entries for TP2, so how can my last incr from TP1 still be valid if it was based on what changed since the previous one for TP2?

George


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--
George Sinclair
Voice: (301) 713-3284 x210
- The preceding message is personal and does not reflect any official or unofficial position of the United States Department of Commerce -
- Any opinions expressed in this message are NOT those of the US Govt. -

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