[This is a meta-answer, because I've heard people say "differential
backup", but I had no darn idea what it meant, and I figure there
might be others out there in the same boat!]
On Wed, Jun 25, 2003 at 08:30:41AM -0300, Roberto Samarone Araujo (RSA) wrote:
> It it possible to use amanda to do diferential backups ? Are there any
> specific configuration ?
AFAICT, there are two meanings to "differential" when you're talking
about backups.
1) Databases. For databases (e.g., Oracle, SQL) you are often backing
up a small number of very large files (and sometimes not files at
all, but raw partitions). In this context, "differential" means
backing up only those blocks within a large file (or raw partition)
that have changed.
This is obviously the realm of a special-purpose backup program,
Amanda itself definitely doesn't know anything about it.
2) Windows file systems. Files on (all?) Windows file systems have an
"archive bit". The intent is that this bit is set when a file is
modified. The intent is that a full backup clears all the archive
bits. In this context:
An "incremental" backup gets files that have changed since the full
or previous incremental, and re-clears the archive bits.
A "differential" backup gets files that have changed since the full,
and leaves the archive bits alone.
So this is sort of a round-about way of getting the same
differences in behavior you get my controlling level in dump.
Strictly speaking, Amanda doesn't know anything about this either.
Since you're apparently a Windows guy, I'm guessing you mean "windows
differential", not "database differential". Is that correct? And then
the answer to your question depends on what type of file system you're
backing up and what underlying backup engine (e.g., tar, dump,
smbclient) you're using.
--
Jay Lessert jay_lessert AT accelerant DOT net
Accelerant Networks Inc. (voice)1.503.439.3461
Beaverton OR, USA (fax)1.503.466.9472
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