Raw Partitions

[Robert Binkhorst]

Hi Hein,

You have a very Dutch name for someone living in the States. Are you an expat or do you have adventurous parents/ancestors?

Anyway, please see the following thread where this is discusses as well.
http://forums1.itrc.hp.com/service/forums/questionanswer.do?threadId=472408

Cheers,

Robert

[Hein van den Heuvel]

Thanks. That does explain it very well.
It makes it perfectly clear that the provided data is meaningless for the problem being discussed.

The deal with raw devices is NOT that they make IO faster. They don't (not directly). It is that they decrease system time, and buffer space wasted on bouble-buffering IOs (both in Oracle and the system).
A measurement of cpu(system) time might have shown that effect.

The better way to accomplish this is 'direct IO' currently available very nicely in Tru64, and being worked on to integrate with the AdvFS/Cluster filessystem in hpux (we have a very early version running since last week. Promissing, but still far out for customer usage).

Anyway it is all a moot point as for this discussion the customer just about _has_ to use raw devices to satisfy Oracle RAC requirements.

[Ja, geboren en getogen brabander. Ik was er vorige week nog. Ik moest tog naar de kapper, en het was carnaval en zo. Met vriendelijke groetjes, Hein)

hth,
Hein.

[A. Clay Stephenson]

Let me give you one more hint when using raw devices with Oracle. Do not use the raw device nodes themselves (e.g. avoid /dev/vg02/rlvol1) but rather use symbolic links (e.g. /oradata/user01.raw) that point to the actual raw device nodes.

Thus, for example, from Oracle's perspective, you would use /oradata/user01.raw
but you would create a softlink
ln -s /dev/vg02/rlvol1 /oradata/user01.raw.

This little bit of indirection adds negligible overhead but it allows you to easily change the physical location of the data with no changes to Oracle. You simply change the link. It also makes it much easier to move the database to a new platform. The benefits are even greater if you are using actual physical disks rather than LVM. You also get a little bit of self-documentation via the ls -l /oradata command.

[Faizer]

Some others have been telling me to use Veritas Cluster Volume Manager with RAW partitions. Any advise on this...