RE: Also now: raw devices on Sun

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Colin Bull - 26 Aug 2004 11:51 GMT

Neil Truby wrote

> (*) We are setting up two new Sun StoreEdge arrays for a new
> Informix installation. These devices come pre-configured as
> RAID-5. Obviously we love and fear Art so much that we
> wouldn't dare not change it! However, reading through the
> performance guide there is a section specifically dealing
> with raw devices, in which it states that raw vs file system
> is now a non-issue and that large and increasing numbers of
> data centres are now just using file system "for very good
> reason". It goes on to say that the Sun UFS type has been
> optimised in recent years and more-or-less implies that you
> shouldn't use raw. Strangely, the text doesn't mention any
> particular DBMS but the headline does mention Oracle.
>
> Any lessons for Informix from this ....

Yes - Do not believe everything ignorant lying sales people tell you.

The company that sold us our SAN sell Oracle. They told us we could not
use raw disk on it.
We did, and we benchmarked it against filesystem. Raw gave us always
15-30% better results.
(They also sold us a PA support contract recently, but that is another
story :-( )

Most kids who set up the expensive RAID systems believe the salesman and
do not try any other way, and use filesystem because they have no
experience of raw disks and are frightened by it.

No doubt you were told there was no point in not using RAID 5 as that is
what the system is optimised for, so why believe them about filesystem.

Let us know the results after you have benchmarked both ways. :-)

Bitter and Twisted
Stevenage

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Neil Truby - 26 Aug 2004 14:07 GMT

> The company that sold us our SAN sell Oracle. They told us we could not
> use raw disk on it.
> We did, and we benchmarked it against filesystem. Raw gave us always
> 15-30% better results.
> (They also sold us a PA support contract recently, but that is another
> story :-( )

Oh yes? Tell me about it ...!

> Let us know the results after you have benchmarked both ways. :-)

Probably won't but will just set it up as raw on the grounds that it'll make
it more difficult to understand what's what and thus perpetuate our support
contract ;-)

> Bitter and Twisted
> Stevenage

I thought you lived in Cornwall?

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superboer - 30 Aug 2004 11:03 GMT

My 2 0.01 on this:

have seen people made mistakes using block mode raw dev instead of
char mode. (they did configure the appropiate # of aiovps!!)
when they restored, the machine was pretty busy AND it took at least
3 times longer to get the lot restored.

So char mode raw is superiour to filesystems!!!! specially on sun.

Besides this: KAIO is what you want not aiovps.

See you

Superboer.

> > The company that sold us our SAN sell Oracle. They told us we could not
> > use raw disk on it.
[quoted text clipped - 15 lines]
>
> I thought you lived in Cornwall?

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