RE: recovery from RAW partitions

From: Powell, Mark D <>
Date: Tue, 17 Jun 2008 09:52:55 -0400
Message-ID: <>


We have used raw partitions for a long time. Generally raw partitions provide 3 to 5% better performance than direct IO which is generally better than the other available IO methods.

At the OS level you need to use 'dd' to backup/copy raw partitions or use rman for you backups.

It makes little sense to use expandable datafiles built on raw partitions which might be one problem your DBA has with using raw partitions.

Also depending on the OS some OS's cannot define a raw partition on the fly so you have to pay attention to your tablespace growth and plan ahead. For some people holding DBA positions this is asking too much.

  • Mark D Powell -- Phone (313) 592-5148

-----Original Message-----
[] On Behalf Of Bobak, Mark Sent: Tuesday, June 17, 2008 12:13 AM
To:; Subject: RE: recovery from RAW partitions

Let's try this again. What does "I was talking to a DBA today who insisted that performing a recovery with a RAW partition." mean? What are you asking for agreement/disagreement on?

As to the performance improvement, if any, of raw devices, well, as with many things, it depends.

Personally, I use raw partitions for the following reasons:

  • AIO and DIO capable
  • no memory wastage caching datafile blocks in filesystem cache
  • Sys admin staff is comfortable w/ raw partitions
  • In my environment, there's no downside


From: [] On Behalf Of Rick Ricky [] Sent: Monday, June 16, 2008 11:01 PM
Subject: recovery from RAW partitions

I was talking to a DBA today who insisted that performing a recovery with a RAW partition. He didn't really explain why. Does anyone agree with this? If so why? He also said that RAW partitions only give about a 2% performance improvement. If so, why would you want to use them (other than with voting disks and OCR in RAC).


Received on Tue Jun 17 2008 - 08:52:55 CDT

Original text of this message