RE: Rman Parallelism param
- From: DENNIS WILLIAMS <DWILLIAMS@xxxxxxxxxxxxx>
- To: "'oracle-l@xxxxxxxxxxxxx'" <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 26 Mar 2004 11:09:48 -0600
Tom
I was told that often a single disk won't stream data fast enough to keep
a high-speed tape drive busy. When the buffer empties, then the tape must
stop, which slows the overall throughput considerably. This was the original
intent of this feature.
We use RMAN to back up to disk, so I can't vouch for the tape business.
On our old system we didn't have enough disk area to hold the entire backup.
At least in 8.1.6 there wasn't a command to split the backup to different
areas. I ran two parallel processes, writing to separate disks and this
nicely split the size nearly in half.
I think whether parallel backup will speed up your backup will depend on
your disk layout. If you can write to more than one storage system, then it
should increase your speed. If you are just writing to a single storage
system, then parallelism might even slow down your throughput because the
disk heads might have to move around more to satisfy both processes.
Ultimately you'll need to test it. Your mileage may vary.
Dennis Williams
DBA
Lifetouch, Inc.
dwilliams@xxxxxxxxxxxxx
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx]On Behalf Of John Hallas
Sent: Friday, March 26, 2004 10:52 AM
To: oracle-l@xxxxxxxxxxxxx
Subject: RE: Rman Parallelism param
What happens when you try it with disk (or even tape). Certainly disk and
sbt are valid parameters to the command.
I am not sure when writing to tape that a parallelism of 4 would speed
things up all that much as the bottleneck will be getting the data onto the
tape via the channels, not reading from disk
Never tried it and just finished a position where I would have had a chance
to - c'est la vie. Hence about 6 posts in 2 days, which equals my previous
6 months worth of contributions.
There are a lot of new config parameters in 9i that do reduce the size of
scripts but I don't necessarily think that was a big overhead anyway. I
think I preferred to see a script with a allocate channel commands and all
the other details in rather than assuming that the parameters had been set
by default
John
-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx]On
Behalf Of Mercadante, Thomas F
Sent: 26 March 2004 16:23
To: oracle-l@xxxxxxxxxxxxx
Subject: Rman Parallelism param
All,
Within Rman, I can : CONFIGURE DEVICE TYPE DISK PARALLELISM 2;
Does anyone know what this does? The docs only mention setting this for
tape. I am hoping that I can spin up several rman backup processes at once
to speed up a disk backup.
any thoughts would be appreciated - thanks!
Tom Mercadante
Oracle Certified Professional
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