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LogicalDisk Object

The Logical Disk performance object consists of counters that monitor logical partitions of hard or fixed disk drives. System Monitor identifies logical disks by their drive letter, such as "C." To monitor Logical Disk object counters, you must activate them by typing the following at the command prompt:

diskperf -yv

Counter Name Description Counter Type
% Disk Time Shows the percentage of time that the selected disk drive is busy servicing read or write requests. PERF_PRECISION_100NS_TIMER
% Disk Read Time Shows the percentage of time that the selected disk drive is busy servicing read requests. PERF_PRECISION_100NS_TIMER
% Disk Write Time Shows the percentage of time that the selected disk drive is busy servicing write requests. PERF_PRECISION_100NS_TIMER
% Free Space Shows the percentage of the total usable space on the selected logical disk drive that is free. PERF_RAW_FRACTION
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 operation from the disk. PERF_AVERAGE_TIMER
Avg. Disk sec/Transfer Shows the time, in seconds, of the average disk transfer. PERF_AVERAGE_TIMER
Avg. Disk sec/Write Shows the average time, in seconds, of a write operation to the disk. PERF_AVERAGE_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 outstanding on the disk at the time that the performance data is collected. It also includes requests in service at the time of the collection. This is a snapshot, not an average over a time interval. 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 will be 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 for good performance. 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 at which read operations are performed on the disk. PERF_COUNTER_COUNTER
Disk Transfers/sec Shows the rate at which read and write operations are performed 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 at which write operations are performed on the disk. PERF_COUNTER_COUNTER
Free Megabytes Shows the unallocated space, in megabytes, on the disk drive. One megabyte is equal to 1,048,576 bytes. PERF_COUNTER_RAWCOUNT

See also

  • Finding Cache Bottlenecks
  • Finding Disk Bottlenecks

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