On Thu, Nov 14, 2002 at 09:46:56AM +1100, Brendan Sandes wrote:
> I'm trying to create a directive on the server that will skip a subdirectory.
> The manual says that skip "omits the specified files and directories from the
> backup" so I'm assuming that it acutally does this.
>
> The situation is that we have a partition /project with two large directories
> (DEV and TEST (about 180GB each) that we want to backup on alternating nights.
OK, you're going to have to be _very_ careful about doing this - Odds are
it's not going to do what you want it to. If you're only ever going to do
full backups you'll be OK (once you get your directives sorted out), but if
you're going incrementals you'll hit problems.
To understand why you need to know how Legato does incrementals. When it
starts a full backup for a volume it stores the time, and marks that as the
savetime for that backup. When it comes along at a later stage to do an
incremental it uses the time of the last full (or incremental) backup,
and backs up everything which has changed since that time. The time this
backup started is again recorded as the savetime for this backup.
So say you've got something like :
Backup 1 - FULL - Friday 20:00
Backup 2 - Incremental - Saturday 20:00
Backup 3 - Incremental - Sunday 20:00
Backup 4 - Incremental - Monday 20:00
Now, if you're backing up the entire /project partition then backup 1 will
contain everything, backup 2 will contain everything modified between 8pm
Friday and 8pm Saturday, backup 3 will be everything modified between 8pm
Saturday and 8pm Sunday, etc.
However, say you change backup 2 to skip /projects/dev and only do
/projects/test, and you change backup 3 to skip /projects/test and only do
/projects/test.
In this case, backup 1 will still get everything.
Backup 2 will get everything in /projects/test which has changed between
Friday 8pm and Saturday 8pm (as expected)
Backup 3 will get everything in /projects/dev which has changed between
SATURDAY 8pm and Sunday 8pm!! ie, everything in /projects/dev which was
modified between Friday 8pm and Saturday 8pm (and not modified again
between Sat 8pm and Sun 8pm) will NOT be backed up!
Legato will not realise that you've change the directives between the
backups, and thus will still only backup whats changed in the last 24 hours-
even though this isn't really an incremental at the directory level, it
is as far as it's concerned.
The result - you'll end up thinking you're backing up everything, and you
won't realise until you come to restore that you're only getting half of
the changes!
It doesn't matter if this is done via one client entry or via two, or
if they are in one group or two - you'll still see this problem.
The only solution I know if is to have the two directories on different
partitions, and then back them up individually as different clients -
without using directives. This works as Networker keeps a track of
savetimes on a per-partition basis.
It may also be possible to just list the directories individually in the
differnet clients (ie, the /projects/dev and /projects/test directories)
and again not use directives - I've never tried this but it might work.
With both of these solutions the biggest problem is that you can no longer
use the "ALL" keyword - you need to manually list all of the fileysystems
on the machine.
Scott.
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