[H-GEN] System Backup Methods

[David Jericho]

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On Tue, Jan 09, 2001 at 10:51:28PM +1000, Michael Anthon wrote:
> As a prefered option, I would like to perform a complete daily system
> backup.  If possible I'd like to do a backup while the database is
> live.  I've previously used ArcServe on NT/Novell systems and this was
> able to do this type of backup, however I've been unable to find
> anything similar for Linux.  If needs be I can shut down most of the
> services and perform a full system backup some time during the night (it
> is, afterall, a development system, not a production system 8^).

Proprietary backup systems are evil(tm).

See the recent SAGE-AU magazine for more info on a story about this :)

We use flexbackup, using the dump mechanism, avaliable from freshmeat. Sure,
no clicky button tools, but it can do network backups, and you can choose from
tar, dump, cpio and afio as your backup methods. And we can restore the data
without having flexbackup avalible, and you don't need to restore the data
from the same machine (as is the case with some oddball systems).

All of our Oracle boxes, be they Sun or Linux, have a spare drive to buffer
the backup, speeding things up a fair bit. We always have run our databases in
archive log mode.

Basic procedure we used to use.

0) Clear oldest backups from buffer drives.
1) Do our hot backup tablespace guff.
2) Backup database files onto buffer drives.
3) Turn off hot backup mode.
4) Copy archive logs to buffer drives after switching to a new log.
5) Copy control files to buffer drives.
6) Dump the buffer drives.

It gives us the advantage that if we do need to restore something that broke
overnight in a hurry, we do have the on a fast disk instead of slow
tape. 

What we do now, is use Enterprise Manager, and do a nightly logical export of the
database to the buffer drive. You can also do this from your sqlplus client. 

0) Clear oldest backups from buffer drives.
1) Issue an export to the buffer drives.
2) Copy control files to the buffer drives.
3) Dump the buffer drives.

We also do a hot backup of database after the original dumps, just as a 
paranoia option. I'm of two minds as to that.

To quote Oracle Press' ``Oracle 8 Backup & Recovery Handbook'' (being a 
650 page handbook ;), "An export of a table will give a read-consistent 
view of the table at the time the export was initiated.  Any changes made 
to the table during the export will not be incorporated into the export file."

If you can stretch the budget far enough, a second scsi controller, with a
second tape unit, and an entirely separate set of tapes might help with the
paranoia factor. Given that tape drives tend to fail without telling you,
it's a Thing That Helps Me Sleep At Night(tm).

I strongly recommend the "Oracle 8 Backup & Recovery Handbook". It's very easy
to read, and the authors cover NT systems, Unix systems with ksh, and VMS
systems if you're unlucky enough to have them. IBSN 0-07-882389-7

-- 
David Jericho, Systems Administrator
WebMatchIT Interactive Marketing

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