RE: Oracle backups using Snapshot Technology

From: Robert Freeman <robertgfreeman_at_yahoo.com>
Date: Wed, 8 Nov 2006 09:19:48 -0700
Message-ID: <KEEDIPJOJLCHPPAIDPDOOEDICMAA.robertgfreeman@yahoo.com>

I've been to a couple of clients that use snapshot technologies (presumably where the hard drive vendor offers the ability to break a mirror and then provides solutions to backup that particular mirror). It's been maybe 4-5 years since I've worked with this technology but it seemed to work ok. How would I compare this to RMAN (hope the formatting comes out ok):

Implementation The snapshot tech No outage required to implement except to
required database I've seen requires that put the database in archivelog mode if

changes               you coalesce the DB.      required.
                      This is effectively an
                      outage (short term)

Feature               Snapshot Available        RMAN Available (10g)
Fast Recovery         Yes - Typically restore   Yes. Several options
including flashback
                      from the snapshot and     database, flash database
restore, backups
                      apply archived redo. As   on disk. These can be as
fast as snapshots,
                      I recall some solutions   in fact flashback could be
faster since
                      actually track change on  there is no need for redo
application.
                      the disk itself so you do
                      not have to apply redo.

Backup Times          Very fast. Generally       Varies. (CPU, Disk speeds,
etc...)
                      requires an outage.        Generally slower.

Database Impacts      Coalesce likely required   RMAN tries to limit IO
impact. If you have
                      (can you put tablespaces   a system that is already
overtaxed, then
                       in hot backup mode        RMAN will make things
worse.
                       instead?) Little overall
                      IO impact.

Tablespace or         I'm not sure if these      Supported.
Datafile Recovery     solutions allow recovery


(online)              of specific files. If

                      they did, could it be
                      done online?

Corrupted block       Not supported              Supported

recovery (online)

Easy database Not supported Supported duplication

Compression of Unsure of this. Supported Backup images

Ease of offsite of Unsure of this. Generally pretty easy if you are using tape.
backups

Instantiation of Not supported Supported standby

Support from your Not supported (AFAIK) Supported Database Vendor
(meaning they will

fix bugs in the
product if found)

There are a few thoughts...

RF

-----Original Message-----
From: oracle-l-bounce_at_freelists.org
[mailto:oracle-l-bounce_at_freelists.org]On Behalf Of DIANNA GIBBS Sent: Wednesday, November 08, 2006 8:45 AM To: oracle-l_at_freelists.org
Subject: Oracle backups using Snapshot Technology

We're looking at implementing a new enterprise backup solution.

Is anyone using "snapshot technology" to backup your oracle databases? If so, could I get more info - O/S, database version, database size, timings for putting tablespaces in backup mode (database mode if 10g), SGA size, good things, lessons learned, comments or thoughts? Have you tested the backup, recovered or refreshed an environment using this technology - any issues?

What about snapshot vs RMAN - any comments?

Thanks in advance.
Dianna Gibbs
Children's Medical Center - Dallas

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Received on Wed Nov 08 2006 - 10:19:48 CST