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Re: RMAN backup optimization

From: Jared Still <>
Date: Wed, 26 Dec 2007 12:04:46 -0800
Message-ID: <>

On Dec 26, 2007 9:57 AM, Suresh Chaganti <> wrote:

> Typically, this job is runnning for 90 minutes to backup about 40GB of
> archive redo.

90 minutes is a long time to backup 40 gig.

How many IOPs can the backup disk support, and is the disk dedicated to backups?
If the disks are not local, how are they attached. 1Gig? Fiber? ?

> There is concern that this RMAN job is hogging too many resources and
> impacting production application performance. I am still in process of
> getting familiar with application and environment.
> ...
> Is 90 Minutes to backup 40GB of archived redo on this box sound normal?

We don't know what your HW/network environment is. But 90 minutes to backup 40 gig seems slow to me.
You listed 32 CPU's, but perhaps your apps are busy using most of that capacity.

> The backup was running on 2 channels, but was recently modified to 6
> channels and users starteed complaining about reduced performance.

Going from 2 compressed backup channels to 6 seems quite leap.

All that compression is apparently causing some systems to bottleneck.

Your job is to find out where the bottleneck is.

Disk IO? CPU?

What is the system load on the CPU's when the backups are running?

What is the service time of the disk system for the database?

> One idea came to my mind is investigate if we are better off moving
> archive destination outside ASM on OCFS or any cluster FS and use OS
> utilities to compress and backup. Any idea if this will be faster than RMAN
> backup

Or you could cut back the number of channels in the backup.

There is a point of diminishing returns when adding channels, and you seem to have found it.

Or turn off compression in RMAN, and backup the files to another server and compress them there.

There are no silver bullets here, you just need to find out what makes your system happy.

Six compressed backup channels apparently makes it unhappy.

Jared Still
Certifiable Oracle DBA and Part Time Perl Evangelist

Received on Wed Dec 26 2007 - 14:04:46 CST

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