RE: ORION num_disks

From: Mark W. Farnham <>
Date: Fri, 12 Sep 2008 06:40:27 -0400
Message-ID: <>

I'm missing why you think the number is not 1.  

I'm curious why 4 LUNs were created - was it merely to keep the total size down for a single LUN? (Some storage mechanisms parcel out various maximum resource amounts per LUN, so there are reasons beyond the size is a single LUN getting scary to carve up a stripe set into multiple LUNs. I'm not aware of per LUN limits like that on Clariions. If there are some I'm always ready to be enlightened.)  

These disks have been linked together as a single interdependent unit of i/o. Think about it this way: Can you predict whether any two simultaneous i/o actions against this set of 4 LUNs will collide on a physical disk?  

You have a single stripe set. (If by your description you mean the disks are pairwise plexed and then striped across the four resulting resilient logical drives, and then those are carved into 4 LUNs. It would be possible from your description to consider a pair of two resilent drive raid groups. Then you would have two independent units of i/o within the Clariion box and possibly beyond depending on how the i/o controllers are set up and whether sharing capacity on them can be nearly ignored [even with 90% headroom on total throughput you'll get some collisions on request initiation.])  



From: [] On Behalf Of LS Cheng
Sent: Friday, September 12, 2008 5:28 AM To: Oracle-L Freelists
Subject: ORION num_disks  


Does anyone know what value should be used for num_disks argument when running I/O stress tests with ORION?  

For example consider I have a RAID Group within an EMC Clariion CX-700 SAN, formed by 8 physical disks and striped using RAID 1+0, then from this RAID Group 4 LUN are created and presented to the server.  

What is the value for num_disks, 8 or 4?  


-- Received on Fri Sep 12 2008 - 05:40:27 CDT

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