RE: asm vs raw - the smackdown
Date: Wed, 27 May 2009 14:09:22 -0400
It's also worth noting that effectively, ASM *is* raw, since the Oracle database still does I/O directly to block devices. ASM just provides that handy dandy metadata layer. Does your vendor have any (good) reasons why they don't want you to use ASM, or for that matter, a filesystem?
[mailto:oracle-l-bounce_at_freelists.org] On Behalf Of Jeremy Schneider Sent: Wednesday, May 27, 2009 2:00 PM
Subject: Re: asm vs raw - the smackdown
> does anyone know of any papers or study comparing ASM vs raw
> performance? We have a vendor deadset on raw, and the DbAs would
> rather not have to deal with that!
From metalink note 754305.1, accessed today: ==> In release 11.2, the Oracle installer and DBCA (Database configuration assistant) will no longer support raw/block devices for database files.
==> As stated in metalink note <578455.1>, Oracle plans to fully desupport RAW/Block device storage effective with the next major release following 11.2. At this time, customers will need to migrate any data files stored on RAW/Block devices to ASM, a cluster file system, or NFS. Thus, we recommend new databases not be deployed on RAW/Block devices.
I couldn't access metalink note 578455 but it is also mentioned here: http://askdba.org/weblog/?p=154
Also, just a technicality, but if you're on Linux then raw access has long been deprecated in favor of direct block access.
I wouldn't expect to see too much difference in performance since ASM is essentially accessing the devices in a "raw" manner. But there are countless other reasons to choose ASM above raw. And I really can't think of a single good reason to choose raw above ASM today. If it were me, I'd continue to strongly argue with the vendor.
-- Jeremy Schneider Chicago, IL http://www.ardentperf.com -- http://www.freelists.org/webpage/oracle-l -- http://www.freelists.org/webpage/oracle-lReceived on Wed May 27 2009 - 13:09:22 CDT