Re: UNIX root backup/SAN disk image vs. Oracle Hot Backups

From: Frank van Bortel <fvanbortel_at_netscape.net>
Date: Thu, 02 Sep 2004 10:05:23 +0200
Message-ID: <ch6jr7$q4$1@news5.tilbu1.nb.home.nl>

Joel Garry wrote:

> idogan_tech_at_yahoo.com (Ibrahim DOGAN) wrote in message news:<6bf58828.0409010559.5ccd70bb_at_posting.google.com>...
>

>>Can UNIX root backup or SAN disk image backup be reliable as Oracle
>>database backup?
>>
>>I don't know internals about root backup or disk images but it sounds
>>like you may end up with inconsistent control file/datafiles when you
>>load them back ?
>>
>>is there anybody out there who knows how root backup/disk image works
>>and can tell whether they can replace Oracle hot backups?
>>
>>Thanks a bunch
>>i.d.

>
>
> As Sybrand sort-of intimated, they must work together. So, it depends
> how fast your mirroring works. The general idea is to
> [triple-]mirror, put all tablespaces into backup mode, break [extra]
> mirror, take out of backup mode, and copy the image at your leisure.
>

Any reason triple is in brackets asif it were optional? If not triple, you are breaking a mirror, which you put there for a reason...
BTW, ever waited for a mirror to be synchronized, in a case where a reasonable (30 GB) sized db was located on the other member? Did bring the backup schedule in jeopardy (AIX 4.3 / 8 CPU S70).

As Joel stated, but did not emphasize enough, it depends how fast your mirroring works.
And I'd like to add: and how much performance impact it imposes on your application!

> Backup mode causes much more writing to logs (look up "fractured
> blocks" in the Oracle docs), so that's why RMAN is better versus
> copying one tablespace at a time over a period of time, it has a much
> lower impact on log writing. Image copies moot that, if they are fast
> enough. Some configurations take a long time to resilver the mirror,
> so, it depends, on transaction load, hardware, requirements, data
> size, etc.
>
> Of course, RMAN has a lot of other benefits that might outweigh a
> naive site-specific mirroring strategy.
>
> jg
> --
> @home.com is bogus.
> Well, shiver me slartibartfast!
> http://news.bbc.co.uk/1/hi/entertainment/tv_and_radio/3615046.stm

-- 

Regards,
Frank van Bortel

Received on Thu Sep 02 2004 - 03:05:23 CDT