Re: RMAN Performance Maladies
- From: "Jared Still" <jkstill@xxxxxxxxx>
- To: MFontana@xxxxxxxxx
- Date: Mon, 12 Feb 2007 14:51:59 -0800
Comments inline
On 2/12/07, Michael Fontana <MFontana@xxxxxxxxx> wrote:
...
SLA, and at this point, incrementals are not an option. However, the
actual runtime to complete a full database backup with RMAN compared to
SqlBackTrack has gone from 30 minutes to over 4 1/2 hours!
...
I am curious as to how your system was backing up 500+ gig in 30 minutes.
Was this due to the compression?
after opening an SR with Oracle support, who seems to believe our
runtime is in the expected range, we still believe something can be done
Seems reasonable to me.
My question is - has anyone actually run RMAN against a large (> 200g)
database right out of the box without tuning?
We run 3 channels to a fairly new tape library. I can't recall the type of
drives,
but they are fairly fast. We use Veritas Netbackup.
Backing up a 700G 9i database takes about 3 hours. With our older
and slower library, it took about 6 hours.
Has anyone spent a great deal of time tuning?
No, future project though.
We are running 4 channels, have an 8 cpu Sunsparc solaris with 16g of
memory, and have experimented with recommended parameter settings for
maxsetsize and maxfilesperset without success. Any information or
assistance or comment would be appreciated, thanks in advance!
You need to determine which you want to maximize, backup performance
or restore performance. When dealing with tape, one is always at the
expense of the other.
Some things to look at are:
* number of channels
* use incremental (level 1+) backups
* filesperset.
Higher = better backup performance (keep the tape streaming)
better restore performance for entire db restores
Lower = Better Restore performance for single files ( no reading large
archives for 1 file)
* tape IO slaves - avoid eating up PGA
See ML Note 388422.1 RMAN best practices
There is also a tuning chapter in the Oracle backup manual.
Don't forget any tuning info for your backup software, the MLM layer that
is.
I'm still curious about those 30 minute backup times with SQL Backtrack.
A 500G database going into 4 channels in 30 minutes is 75meg per second.
There must be some very fast compression going on somewhere, or you
have some really fast drives.
HTH
--
Jared Still
Certifiable Oracle DBA and Part Time Perl Evangelist
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