Re: Cluster file systems versus raw devices in Oracle RAC

If CFS'es were all fantastic, then there'd be no need for raw. But CFS'es can be a real pain, and you'd better believe you'll have another layer of complexity on your hands no matter which one you choose. And some of them don't really qualify as CFS, but only as C(luster), since not everything can move under the CFS umbrella, and thus it's not really an FS.

As for performance, there can be benefits had from going raw. And the opposite. It depends.

Mogens



Antonio Belloni wrote:

Hi,

Does anyone using cluster file systems in a RAC 10gR2
installation, specifically IBM’s GPFS?

I’ve visited a company that is running RAC 10gR2 in
AIX over raw devices. Why someone would choose to use
raw devices , with all the problems to administer ,
when all the modern file systems are so powerful? Is
there any issues when using cluster file systems +
RAC? Is there considerable performance benefits when
using raw devices with RAC ?

I´ve always used Oracle stand alone instances over
file systems (since version 7) , and performance was
always very good. I´ve tested raw devices almost 10
years ago , and even in that time (the hardware today
is much better - SAN , 15K rpm disks , huge caches -
and the file systems software today is much better)
the cost to administer it does not compensate the
benefits (only 5% more faster than file systems in
Oracle 7). 

So , as I didn't see a line in the Oracle RAC
documentation saying that RAC only works over raw
devices and besides any limitations imposed by RAC ,
why use raw devices nowadays ?

Regards,
Antonio Belloni





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