Physical Disk

The Physical Disk window shows information about the disk.

The grid located at the top of the window shows each individual disk with the following information for each one:

% Disk Time Percentage of elapsed time that the selected disk drive was busy servicing read or write requests.
Queue Length Number of requests outstanding on the disk at the time the performance data is collected. It also includes requests in service at the time of the collection. Multi-spindle disk devices can have multiple requests that are active at one time, but other concurrent requests are awaiting service. This counter might reflect a transitory high or low queue length, but if there is a sustained load on the disk drive, it is likely that this will be consistently high. Requests experience delays proportional to the length of this queue minus the number of spindles on the disks. For good performance, this difference should average less than two.
Avg. Disk KBytes/Transfer Average number of kilobytes transferred to or from the disk during write or read operations.
Disk Transfers/sec Rate of read and write operations on the disk.
Avg. Disk Time/Transfer The time, in milliseconds, of the average disk transfer.
Split IO/Sec Rate at which I/Os to the disk were split into multiple I/Os. A split I/O may result from requesting data of a size that is too large to fit into a single I/O or that the disk is fragmented.

By default, the last snapshot is displayed in the grid. Use the slidder (or the arrow buttons) located at the top of the grid to navigate through the collected snapshots. In monitoring, the "Auto-Update" button must be unchecked to be able to navigate through the collected snapshots.

Select one or more disks in the grid (Check box at the left of the grid) to update the graphes located at the bottom of the window. If several disks are selected, the statistics are aggregated.

% Disk Time

transfer Percentage of elapsed time that the selected disk drive was busy servicing read or write requests.
read Percentage of elapsed time that the selected disk drive was busy servicing read requests.
write Percentage of elapsed time that the selected disk drive was busy servicing write requests.

Queue Length

Number of requests outstanding on the disk at the time the performance data is collected. It also includes requests in service at the time of the collection. Multi-spindle disk devices can have multiple requests that are active at one time, but other concurrent requests are awaiting service. This counter might reflect a transitory high or low queue length, but if there is a sustained load on the disk drive, it is likely that this will be consistently high. Requests experience delays proportional to the length of this queue minus the number of spindles on the disks. For good performance, this difference should average less than two.

Avg. Disk KBytes/Transfer

transfer Average number of kilobytes transferred to or from the disk during write or read operations.
read Average number of kilobytes transferred from the disk during read operations.
write Average number of kilobytes transferred to the disk during write operations.

Disk Transfers/sec

Rate of read and write operations on the disk.

Avg. Disk sec/Transfer

Time, in seconds, of the average disk transfer.

Split IO/Sec

Rate at which I/Os to the disk were split into multiple I/Os. A split I/O may result from requesting data of a size that is too large to fit into a single I/O or that the disk is fragmented.

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