Re: Replicated File System Consistency

From: DA Morgan <>
Date: Fri, 02 Jan 2009 14:19:18 -0800
Message-ID: <>

Pat wrote:
>> 4. How is the cache configured? What percentage read? What percentage write?

> 8G cache on each head unit (2 head units), but I don't know how its
> configured. Frankly didn't even realize you could configure different
> read/write percentages. I supect the SAN guys know though; is it worth
> asking? Is there a recommendation as to how the cache should be
> allocated? Our workload is very read heavy so I'd naively assume a
> bigger read cache would be preferable.

Configure 100% as read cache. Then test.

>> 5. How many physical disks are you striped over for your hottest data files?

> 30 Fiber Channel 15k drives on each of the main data aggregates.
> All the numbers point to the SAN being much faster, but I think
> what we basically proved is that we don't have an IO bound workload.

That is certainly what it sounds like.

> FWIW the main reason we went SAN wasn't throughput, but crash
> recovery. If a DB server explodes, I can mount its 3 LUNS on a hot
> spare and have it back up in a matter of minutes. Since nobody wanted
> to pay for dataguard, its the best hot failover strategy we could come
> up with.

Data Guard, assuming you have Enterprise Edition, is free. <g>

Daniel A. Morgan
Oracle Ace Director & Instructor
University of Washington (replace x with u to respond)
Puget Sound Oracle Users Group
Received on Fri Jan 02 2009 - 16:19:18 CST

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