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PhysicalDisk Object

The PhysicalDisk performance object consists of counters that monitor hard or fixed disk drives on a computer. Disks are used to store file, program, and paging data, are read to retrieve these items, and are written to record changes to them. The values of physical disk counters are sums of the values of the logical disks (or partitions) into which they are divided.

Counter Name Description Counter Type
% Disk Read Time Shows the percentage of time that the selected disk drive is busy servicing read requests. PERF_PRECISION_100NS_TIMER
% Disk Time Shows the percentage of elapsed time that the selected disk drive is busy servicing read or write requests. PERF_PRECISION_100NS_TIMER
% Disk Write Time Shows the percentage of elapsed time that the selected disk drive is busy servicing write requests. PERF_PRECISION_100NS_TIMER
Avg. Disk Bytes/Read Shows the average number of bytes transferred from the disk during read operations. PERF_AVERAGE_BULK
Avg. Disk Bytes/Transfer Shows the average number of bytes transferred to or from the disk during write or read operations. PERF_AVERAGE_BULK
Avg. Disk Bytes/Write Shows the average number of bytes transferred to the disk during write operations. PERF_AVERAGE_BULK
Avg. Disk Queue Length Shows the average number of both read and write requests that were queued for the selected disk during the sample interval. PERF_COUNTER_LARGE_QUEUELEN_TYPE
Avg. Disk Read Queue Length Shows the average number of read requests that were queued for the selected disk during the sample interval. PERF_COUNTER_LARGE_QUEUELEN_TYPE
Avg. Disk sec/Read Shows the average time, in seconds, of a read of data from the disk. PERF_PRECISION_100NS_TIMER
Avg. Disk sec/Transfer Shows the average time, in seconds, of a disk transfer. PERF_PRECISION_100NS_TIMER
Avg. Disk sec/Write Shows the average time, in seconds, of a write of data to the disk. PERF_PRECISION_100NS_TIMER
Avg. Disk Write Queue Length Shows the average number of write requests that were queued for the selected disk during the sample interval. PERF_COUNTER_LARGE_QUEUELEN_TYPE
Current Disk Queue Length Shows the number of requests that are outstanding on the disk at the time that the performance data is collected. It includes requests in service at the time of the collection. This is a snapshot, not an average over the time interval. It includes requests in service at the time of the collection. Multispindle disk devices can have multiple requests 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 is consistently high. Requests experience delays proportional to the length of this queue minus the number of spindles on the disks. This difference should average less than two. PERF_COUNTER_RAWCOUNT
Disk Bytes/sec Shows the rate at which bytes are transferred to or from the disk during write or read operations. PERF_COUNTER_BULK_COUNT
Disk Read Bytes/sec Shows the rate at which bytes are transferred from the disk during read operations. PERF_COUNTER_BULK_COUNT
Disk Reads/sec Shows the rate of read operations on the disk. PERF_COUNTER_COUNTER
Disk Transfers/sec Shows the rate of read and write operations on the disk. PERF_COUNTER_COUNTER
Disk Write Bytes/sec Shows the rate at which bytes are transferred to the disk during write operations. PERF_COUNTER_BULK_COUNT
Disk Writes/sec Shows the rate of write operations on the disk. PERF_COUNTER_COUNTER
% Idle Time Shows the percentage of time that the disk was idle during the sample interval. PERF_PRECISION_100NS_TIMER
Split IO/Sec Shows the rate at which that I/O requests to the disk were split into multiple requests. A split I/O may result from requesting data in a size that is too large to fit into a single I/O or that the disk is fragmented on single-disk systems. PERF_COUNTER_COUNTER

See also

  • Finding Disk Bottlenecks

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