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How to measure physical disk activity ?


How to measure physical disk activity ?

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Alan Spillert
Alan Spillert
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I am setting up a new server (Windows Server 2008 R2) to run a SQL Server (2012) and IIS (7.5) based web application which manages about 160GB of data (SQL and flat files). I've got 6 large SAS disks in three RAID-1 sets, and have divided the data load, I think, between them. My goal is to optimize performance by splitting up the IO activity across the disks during the work day.

How can I measure my strategy? I'd like to measure disk physical activity without damaging application performance too much.

I'm looking for pointer to a utility or PowerShell script that will measure total IO by disk during a period of a few hours.

Thank you for any assistance.



John Mitchell-245523
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Quite difficult, if you don't have anything to compare your results with. I suppose if users are happy, performance is acceptable. I would recommend monitoring Disk Reads and Writes per sec and Disk secs per Read/Write for each disk. Save the results, and then if you have any problems in future, you can monitor the same thing again to determine whether IO is the problem.

John
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You might also track some of the existing waits with regards to IO. http://www.sqlskills.com/blogs/paul/how-to-examine-io-subsystem-latencies-from-within-sql-server/

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Alan Spillert
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Thank you for the Paul Randall blog - it will be helpful.

I tested a new SAN by running SQLIO every hour from a VM server for several months, and looked at the IOPS change over time as more systems were moved to it. I'm looking to do something similar, by disk drive, on the new server. I might want to move my TEMPDB, or split the SS12 database between drives if I can show improved performance.

On the other hand, I am reluctant to change a system to solve a problem I don't have. This new HP DL380 is giving me over 110,000 IOPS from SAS drives in RAID-1 configuration, and has plenty of memory and CPU.



Alexander Suprun
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Alan Spillert (7/18/2013)
I've got 6 large SAS disks in three RAID-1 sets, and have divided the data load, I think, between them. My goal is to optimize performance by splitting up the IO activity across the disks during the work day.
I'm hardly a RAID specialist, but isn't it better to create just 1 big RAID-5(or 6)? If you do that then the data load will be automatically divided evenly.


Alex Suprun
Alan Spillert
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Yes, data will be divided, but IO activity will also hit all the drives. My attempt is to optimize application performance by spreading out the IO activity.



Alexander Suprun
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Alan Spillert (7/19/2013)
Yes, data will be divided, but IO activity will also hit all the drives. My attempt is to optimize application performance by spreading out the IO activity.
If data is divided then IO activity is also divided, isn't it?


Alex Suprun
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