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Raid 10 – Physical Disk Counter

Hi,<br /><br />Can anyone help clarify something for me?<br /><br />If I have a disk array with 12 disks setup as a RAID 10 would I need to divide the Avg Disk Queue Length performance counter by 12? Or would I divide by 6 since only 6 of the drives are striped? (the other 6 serving as the mirrored array)<br /><br />Also, does the % Disk Time counter need to be divided by the number of disks too?<br /><br />Thanks for any help you can provide! [<img src=’/community/emoticons/emotion-2.gif’ alt=’:D‘ />]<br /><br /><br />Enrique Pasos<br />Application Support Manager<br />Heald College
For example, if you have an array of 6 physical disks, and the Avg. Disk Queue Length is 10 for a particular array, then the actual Avg. Disk Queue Length for each drive is 1.66 (10/6=1.66), which is well within the recommended 2 per physical disk. Check: http://www.sql-server-performance.com/performance_monitor_counters_io.asp Luis Martin
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Yes, thanks, I understand how the calculation should be done, but I’m not sure about how many disks I should use in it. My RAID 10 had 12 disks in it so should I use that number? The more I know, the more I realize how much I don’t know.
Yes, you should use 12.
Luis Martin
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Bertrand Russell
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So does this same logic hold true on a SAN. We have a SAN (Raid 5) with 144 drives in it, the data is spread accorss all the drives. We get avg Q lengths from 2 to 1500? Do we divide this number by 144?
Hi All, We have got SAN with RAID 10. Current setup includes everything (OS files, SQL server, data) in the SAN. Our application server (SQL server box) does not have any disk space at all and only 1.9GB of memory (1.5 allocated to SQL Server). so my question is whether we should request separate physical diskspace to separate the os and e.g. transaction log into separate partitions rather that having them within the raid 10 setup. Will this work anyway and and how big is the administartion overhead in terms of recovery? newbie
Akus Please do not duplicate the question, check replyhttp://www.sql-server-performance.com/forum/topic.asp?TOPIC_ID=8600 here. Satya SKJ
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