Re: [Networker] What level is a differential backup?

Level backups back up "files that have changed since the last backup with a
lower-numbered backup level." A Full backup is level 0. You could implement
a differential backup with a Full and subsequent Level Ns, if N is constant.

You could also do layered differentials, e.g.:

Week 1:
Full
    Level 5
    Level 5
    Level 5
    Level 5
    Level 5
    Level 5

Weeks 2,3,4:
  Level 3
    Level 5
    Level 5
    Level 5
    Level 5
    Level 5
    Level 5

The first week, each level 5 backs up everything that has changed since the
Full, as a classic "differential" would. In subsequent weeks, the Level 3s
back up everything that has changed since the Full. The Level 5s, though,
back up those files that have changed since the most recent Level 3.

With a model like this, you would need at most three savesets to restore to
a particular point in time: one full, possibly one level 3, and one level 5.

There are some pretty pictures in the Admin Guide, Chapter 4, Backup Levels.

Hope that helps

--Geoff


Geoffrey Duke
802.656.1172 | System Administrator | Enterprise Architecture &
Administration | University of Vermont



-----Original Message-----
From: EMC NetWorker discussion [mailto:NETWORKER AT LISTSERV.TEMPLE DOT EDU] On
Behalf Of MIchael Leone
Sent: Wednesday, February 20, 2008 3:00 PM
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Subject: [Networker] What level is a differential backup?

Backup levels are confusing me. Here's what I want - Full backup on Fri, 
differential on Mon - Thu. I use the standard definition of a differential 
- any file that has changed since the last FULL backup.

On my schedule, the full is easy enough. But the description of 
"incremental" - "Backs up files that have changed since the last backup, 
regardless of level. " sounds a lot like differential. Or is differential 
a level 1 - "A level 1 backup backs up all files that have changed since 
the most recent full backup (considered a level zero).". This sounds 
exactly like a differential to me. :-)

So do a do a FULL on Fri, and a level 1 on Mon - Thu? Or is it 
incremental?

Confusedly yours
Mike
-- 
Michael Leone
Network Administrator, ISM
Philadelphia Housing Authority
2500 Jackson St
Philadelphia, PA 19145
Tel:  215-684-4180
Cell: 215-252-0143
<mailto:michael.leone AT pha.phila DOT gov>

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