Hi there, I'd like some advice on disk monitoring - we are using EMC SAN on our SQL servers. We are finding some exceedingly high disk queue length 20+ figures on our DB disks, we already have them seperated onto different LUN's. After doing some searching on the net was advised best method for monitoring SAN storage with various LUN's was to use Logical DIsk - Avge disk sec/transfer http://www.r71.nl/kb/technical/185-disk-queue-length-vs-disk-latency-times-which-is-best-for-measuring-database-performance and also some MS docs http://technet.microsoft.com/en-us/library/aa997558%28EXCHG.65%29.aspx so after reading those seems using "avge disk sec/transfer" seems more appropriate with the figures referenced in the links as reference. However w've come across another issue, while the default Win2k3/8 perf monitor can capture this information, we are using "mount points" and it seems perf monitor cannot monitor these disks counters - is this true and if so are there any alternative methods of monitoring? Much appreciated.Momo

Hi, What model storage are you running? Symm/Clariion? Martin

You could use "Physical Disk" counters instead of Logical Disk. C Shane Cribbs http://www.georgiatechnologies.com

Hi Guys, Were using EMC Clariion and secondly how can I use "physical/logical" disk counters to measure "Mount points"? Cheers.... Momo

We are finding some exceedingly high disk queue length 20+ figures on our DB disks, we already have them seperated onto different LUN's. You've havne't actually said you have a performance issue, and what that is. This counter may not meaning anything, but given your EMC SAN, i think this counter may be an indication of a potential issue, only if you have a performance issue to go along with it. Read this article: http://networkadminkb.com/Shared%20Documents/Disk%20IO%20Tutorial%20Part%201.aspx Avg Disk sec/read and Avg Disk sec/write are the two best counters to use. In general you want single digits here .001-.009 on average. If you are seeing values in the 30's (.030) you have slowness you should address.

Physical disks are physical disks no matter where you have them mounted. That's why I said to use Physical disk counters instead of Logical disk counters. One note, physical disk counters are disabled by default. You can find information on enabling those counters here: http://social.msdn.microsoft.com/Forums/en/winserver2008appcompatabilityandcertification/thread/151a8cbe-6b21-4f7f-b988-6c5015070662 C Shane Cribbs http://www.georgiatechnologies.com

Hi All, Thanks for the valuable information - the only problem is I'm not sure how to measure these values if I'm using mount points, for our SQL servers we setup several 2 drives with several mount points attached and were not sure how to get the performance statistics from those different mount points. Many thanks.Momo

the only problem is I'm not sure how to measure these values if I'm using mount points You must use physical disks, but in performance monitor mount points are just logical numbers. I used these commands to help determine the logical numbers to monitor for mount points. diskpart list volumes In my environment i determine the numbers were off by two because of 0=dvd, 1=hidden 100GB partition, so c=2, while in Perfmon C=0, and the Dvd and 100GB was offline.

If you are using an EMC clarion storage array, you will more than likely need to engage your local EMC tech, the EMC management software has specific interfaces into the EMC's that the standard counters cannot see. With that it can provide you detailed heat maps of your lun and disk usage in the system. Been down this road, and was the only way to nail down the usage stats correctly-- :P Advice offered, If you need more help it is advised to seek the council and advice of paid professionals. The answer is always 42, or reboot.