I am currently wrestling with whether to implement 'rman disk backups' or
'rman tape backups'.
I have put together the following PRO's and CON's list so that I can weigh
my options.
I am putting this out to those on the list that are working with RMAN and
care to add to the points i have made.
It is open for discussion - I look forward to reading your responses.
PS : Either CC me on all question responses or I will get back to you on
Monday - I am currently in Oracle-L digest mode.
Thanks
TAPE
With this option rman directs the rman backup directly to tape.
PROs
- Disk Maintenance issues are not applicable ;
You do not have to be concerned about whether you have enough disk space for
your backups.
You do not have to setup, maintain and monitor daily cleanup jobs.
- Rman will be able to automate the recovery process for you ;
Rman knows where the backups reside (tape) and will recover them to disk -
as needed by the recovery process.
- Setting up a hourly remote copies of any new archive logs is easy - just
setup a tape archive copy.
CONs
- Recovery is slower (disk verse tape).
- When duplicating your database to a different server or in a true
disaster, where you have lost a server and you need to rebuild the instance
on a new server - You will have the added task (and time) of installing and
configuring the Media Management Layer (ie; Legato). Since your backups
reside on tape, the Media Management layer on the Oracle Server needs to be
installed and configured before you can talk with the backup server.
- You have to concern yourself about tape resource issues ;
A 'CROSSCHECK' or 'VERIFY' of your backup may keep the tape subsystem busy
loading, unloading and positioning tapes. If your tape subsystem is used
for other purposes other then your backup - then you could run into
resourcing issues around when and if you should be running these jobs.
- Also the submitting and scheduling of these tape backup jobs will probably
move out of the dba's control (cron) and into the tape management scheduling
group's control.
- With this option you must be use rman "Backups". Rman "Image copies" can
not be directed to tape.
DISK
With this option rman directs the rman backup directly to disk.
All of the Disk Pro's and Con's that I came up with were just the mirror
image of the Tape Con's and Pro's.
The catch with this option is you probably do not have enough disk space to
store all of your backups on disk, therefore you will need to put into place
a procedure that backs up your rman backup files to tape and then deletes
them from disk. Note that rman will still think that all of these backups
still reside on disk therefore it will become the dba's job to manage the
"backup-to-disk", "delete-from-disk" and the "recovery-from-tape" of these
rman backup datasets.
PROs
- Recovery is faster (disk verse tape) as long as the backup you want
resides on disk.
- When duplicating your database to a different server or in a true
disaster, where you have lost a server and you need to rebuild the instance
on a new server - You will not have the added task (and time) of installing
and configuring the Media Management Layer (ie; Legato Client). You would
use standard tape recovery procedures to recover your backups from tape -
then issue the rman recovery commands.
- You do not have to concern yourself about tape resource issues ;
You can schedule a 'CROSSCHECK' or 'VERIFY' of your backup without worrying
about impacting other outside resources.
- The dba is in total control of the tape backup scheduling.
- With this option you can use rman "Backups" or "Image copies".
CONs
- Disk Maintenance issues are applicable ;
You have to be concerned about whether you have enough disk space for your
backups.
You have to setup, maintain and monitor daily cleanup jobs.
- If the backup you want is not on disk Rman will not be able to automate
the recovery process for you ; Rman thinks that all the backups reside on
disk - he does not know that you have backed them up to tape and removed
them from the backup directory. Therefore it becomes the dba's job to
manage theses tasks.
- Setting up a manual hourly remote copy of any new archive logs is more
complex. This will give the dba more tape backups that he will have to
manage and keep track of.
Patrick J. Howe
Oracle DBA
Illuminet. A Verisign Company.
4501 Intelco Loop SE
Olympia, WA 98507
Phone : 360.493.6284
Email : phowe_at_verisign.com
--
Please see the official ORACLE-L FAQ: http://www.orafaq.com
--
Author: Pat Howe
INET: phowe_at_Illuminet.com
Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051
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Received on Fri May 31 2002 - 16:05:02 CDT
