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[oracle-l] Re: The Holy War: Disks

Date: Tue, 27 Jan 2004 10:31:24 -0600
Message-ID: <0186754BC82DD511B5C600B0D0AAC4D607AFFDF8@EXCHMN3>


   RAID5? Dennis Williams
Lifetouch, Inc.

-----Original Message-----
From: Koivu, Lisa [] Sent: Tuesday, January 27, 2004 10:11 AM To:
Subject: [oracle-l] The Holy War: Disks

Hello everyone,  

Windows 2003, v9204, 2 Clariion SANs  

I have just been given ~1tb of disk on a new SAN. The engineer wanted to give me 3 huge (maxed out) disks, 2 350GB and a third with the remainder. I argued for 6 disks similarly sized.  

My fellow DBA supported my argument. The engineer and the dw architect wanted 3 disks.  

I am going to have i/o problems no matter what. Concatenating 10 physical disks into 1 logical disk is going to have as much i/o latency percentagewise as 6 physical disks concatenated into 1 logical disk.  

Each disk has 1 bus, so to speak. These buses are concatenated together into 1 "device". (I'm being told that "device" is a unix term and it doesn't apply in Windows). So, concatenating 10 disks (and buses) together for 1 high speed disk is going to result in having even more data on the other side of the "straw".  

I strongly feel if I have 3 disks instead of 6, my options for alleviating i/o contention are very limited. Any i/o balancing would be messier and more difficult. We are going with 6 disks instead of 3 with the understanding that when we add more disk to this server, we'll evaluate performance of the 6 disks and reconsider.  

As far as I know, the Clariion SANs don't have the whizbang functionality of the Symmetrix that allows moving datafiles at the physical level within the SAN to alleviate i/o hotspots. I also don't buy the argument that the SAN cache should alleviate i/o problems. This is a data warehouse that has the potential to become enormous and it will blow the size of any SAN cache during data loads, guaranteed.  

Is anyone in this type of environment? What have your experiences been? Any and all comments are welcome.  

Thank you  

Lisa Koivu
Senior Monkey

Cendant Timeshare Resort Group

Orlando, FL, USA    

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Received on Tue Jan 27 2004 - 10:31:24 CST

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