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

Actually, as a person who writes quite a bit on the subject, I do not
like (and therefore do not use) the term "differential."  While your
usage may fit the traditional use of the word, there's one big problem
with it. It's called Microsoft.  They've messed up the meaning of the
word, like they've messed up a lot of things over the years.  (Adopt,
Adapt, Extenguish.)  THEIR definition of a differential is as follows:

"A differential backup copies files created or changed since the last
normal or incremental backup. It does not mark files as having been
backed up (in other words, the archive attribute is not cleared). If you
are performing a combination of normal and differential backups,
restoring files and folders requires that you have the last normal as
well as the last differential backup."

Therefore, a Windows differential only acts the way you're describing if
you perform ONLY differentials.  If you perform a single incremental
backup, the next differential will act just like an incremental.

NetWorker's levels are a lot more "classic" than the term differential
backup.  They stem from the levels of the "dump" program on Unix, which
was introduced in BSD Unix sometime in the late 70s or early 80s, 5-10
years before Windows came out.

FWIW, NetBackup calls THEIR incremental a "differential incremental,"
which cracks me up.  What you're calling a differential, they call a
"cumulative incremental."  While it's not a commonly used term, I prefer
it to differential because it hasn't been corrupted by Microsoft.

I also like NetWorker's defined levels.  Even if you perform a level 1
followed by a level 2, you can always come back and get a level 1.

---
W. Curtis Preston
Backup Blog @ www.backupcentral.com
VP Data Protection, GlassHouse Technologies 

> -----Original Message-----
> From: EMC NetWorker discussion [mailto:NETWORKER AT LISTSERV.TEMPLE DOT EDU]
On
> Behalf Of MIchael Leone
> Sent: Thursday, February 21, 2008 8:12 AM
> To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
> Subject: Re: [Networker] What level is a differential backup?
> 
> EMC NetWorker discussion <NETWORKER AT LISTSERV.TEMPLE DOT EDU> wrote on
> 02/20/2008 05:10:22 PM:
> 
> > On Wed, Feb 20, 2008 at 04:38:58PM -0500, MIchael Leone wrote:
> > > > Incrementals only back up the changes for that one day.  Monday
> > > > incremental backs up Mondays changes.  Tuesdays backup does just
> > > > Tuesdays changes.
> > >
> > > Yes, I know. What I don't know is why NetWorker doesn't make it
easy
> and
> > > just have those as pre-defined levels ... they are standard terms,
> after
> > > all ... I always disliked incrementals - too many restores to get
back
> to
> > > where you need to be (to recover all files).
> >
> > I don't understand.  What standard term would you use for
incrementals?
> > All the regular levels are differentials.
> 
> Not a term for incrementals; they have a pre-defined level called
> "incremental", but don't have one called "differential". I realize
that
> the numbered levels server the same purpose, but if the classic term
is
> "differential", why not use it? They use the other classic term of
> "incremental".
> 
> Anyways, I believe I get it now. Thanks.
> 
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