SQL Counter: Part 5 (Disk Queue Length)
PhysicalDisk Object -> Avg. Disk Queue LengthThis counter measures whether I/O requests are being serviced or are waiting in the queue for the disk drive to catch up on requests. This can be a bottleneck in performance for a server in that, if it grows large or is consistently above eight for a particular disk, then that disk device cannot keep up with the arrival of new I/O requests. This can also sometimes depend on the type of disk system one is using.