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rerichards
Starting Member
10 Posts |
 Posted - 2006-01-25 : 21:15:43
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| If I return the Average, Minimum, and Maximum values for the counter Physical Disk: Avg. Disk Queue Length, and those values are 1, 0, 9 respectively, which value do I use to compute the Avg. Disk Queue Length for a 6 disk array: Average, Minimum, or Maximum? |
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eyechart
Master Smack Fu Yak Hacker
3575 Posts |
Posted - 2006-01-25 : 21:51:27
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| are you running a software RAID? Or a hardware RAID?If you are running a hardware RAID then perfmon is not going to know that your Drive F: is actually a RAID comprised of 6 disks. It is going to think that it is a single physical drive. This means that you don't need to worry about calculating what the real average is, since perfmon is giving you the real average.btw, you should probably use current disk queue length instead. I have found this counter to be more useful counter then using the averages.-ec |
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rerichards
Starting Member
10 Posts |
Posted - 2006-01-25 : 22:01:27
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quote:
Originally posted by eyechart
are you running a software RAID? Or a hardware RAID?...btw, you should probably use current disk queue length instead. I have found this counter to be more useful counter then using the averages.-ec
I have never heard of software RAID, I just know we have a RAID configuration of 6 physical disks.Regarding the Physical Disk: Current Disk Queue Length, I return the following Average, Minimum, and Maximum values: 4, 0, 208.Can I take this as a bottleneck problem since "A consistent disk queue length of 2 per disk indicates a bottleneck on the disk."?? |
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eyechart
Master Smack Fu Yak Hacker
3575 Posts |
Posted - 2006-01-25 : 22:15:35
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| current disk queue is a snapshot of the outstanding I/O requests for a given physical/logical drive.Since this is a hardware RAID, your physical and logical drives are most likely one in the same. If you were using a software RAID, you would have had to install multiple physical drives into your server and then use windows disk manager to format them into a logical RAID volume. Your system would still see that you have 4 physical drives installed (just an example), so you could use the physical counters for those 4 drives. You would use the logical counter for the RAID volume that you formatted - drive F: for example. Not many people run this kind of configuration these days.I use the logical counters becuase in some situations we have concatenated two or more physical LUNs presented from my SAN together to form one logical drive letter. We do this to extend the size of a volume. If, for example, I started with a 100GB LUN for a database. If the database grew in size and I needed to add more space, I would have our disk guys present another 100GB LUN to my server. I then would use the disk manager (veritas in our case) to concatenate the two physical LUNs together as a single drive letter. This is the logical volume. The physical volume are the two LUNs we spanned. Keep in mind that in the SAN the physcial LUNs might actually be made up of more than 2 physical disks. Windows however, is only going to see them as 2 physical disks instead of the 12 that really make the LUNs up in the SAN.It is probably a good idea to use the logical counters instead of the physical counters, but you need to be aware of what the differences are.I would only be concerned about the disk if the current disk queue were at some sustained level and never went down to zero. If they were sustained at 10 or more for several minutes then that could be an indication of a disk bottleneck. It could also be an indication that you have a query tuning issue and/or an undersized buffer cache.-ec |
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Physical Disk: Avg. Disk Queue Length