The disk metric group tracks statistics for disk input/output (I/O) performance.

Disk I/O counters support metrics for both physical devices and virtual devices. A host reads data from a LUN (logical unit number) associated with the physical storage media. A virtual machine reads data from a virtual disk, which is the virtual hardware presented to the Guest OS running on the virtual machine. The virtual disk is a file in VMDK format.

Disk Data Counters lists the disk data counters.

Note

Some counters listed in Disk Data Counters subsume other counters. For example, kernelLatency includes both queueReadLatency and queueWriteLatency and the disk usage statistic include both read and write statistics. In addition, only a subset of the disk counters appear in the overview performance charts. To view all disk data counters, use the advanced performance charts.

Disk Data Counters

Counter

Label

Description

Entity

V

H

R

C

commands

Disk Commands Issued

Number of SCSI commands issued during the collection interval.

Stats Type: delta

Unit: number

Rollup Type: summation

Collection Level: 2

VC/ESX: Yes/Yes

ο

ο

commandsAborted

Disk Command Aborts

Number of SCSI commands aborted during the collection interval.

Stats Type: delta

Unit: number

Rollup Type: summation

Collection Level: 2

VC/ESX: Yes/Yes

ο

ο

deviceLatency

Physical Device Command Latency

Average amount of time, in milliseconds, to complete a SCSI command from the physical device.

Stats Type: absolute

Unit: millisecond

Rollup Type: average

Collection Level: 2

VC/ESX: Yes/Yes

o

ο

ο

deviceReadLatency

Physical Device Read Latency

Average amount of time, in milliseconds, to complete read from the physical device.

Stats Type: absolute

Unit: millisecond

Rollup Type: average

Collection Level: 2

VC/ESX: Yes/Yes

o

ο

ο

deviceWriteLatency

Physical Device Write Latency

Average amount of time, in milliseconds, to write to the physical device (LUN).

Stats Type: absolute

Unit: millisecond

Rollup Type: average

Collection Level: 2

VC/ESX: Yes/Yes

o

ο

ο

kernelLatency

Kernel Disk Command Latency

Average amount of time, in milliseconds, spent by VMkernel processing each SCSI command.

Stats Type: absolute

Unit: millisecond

Rollup Type: average

Collection Level: 2

VC/ESX: Yes/Yes

o

ο

ο

kernelReadLatency

Kernel Disk Read Latency

Average amount of time, in milliseconds, spent by VMKernel processing each SCSI read command.

Stats Type: absolute

Unit: millisecond

Rollup Type: average

Collection Level: 2

VC/ESX: Yes/Yes

o

ο

ο

kernelWriteLatency

Kernel Disk Write Latency

Average amount of time, in milliseconds, spent by VMKernel processing each SCSI write command.

Stats Type: absolute

Unit: millisecond

Rollup Type: average

Collection Level: 2

VC/ESX: Yes/Yes

o

ο

ο

maxTotalLatency

Highest Disk Latency

Highest latency value across all disks used by the host. Latency measures the time taken to process a SCSI command issued by the guest OS to the virtual machine. The kernel latency is the time VMkernel takes to process an IO request. The device latency is the time it takes the hardware to handle the request.

Total latency = kernelLatency + deviceLatency

Stats Type: absolute

Unit: millisecond

Rollup Type: average

Collection Level: 1

VC/ESX: Yes/Yes

ο

ο

ο

numberRead

Disk Read Requests

VM

Number of times data was read from each virtual disk on the virtual machine.

Host

Number of times data was read from each LUN on the host during the collection interval.

Stats Type: delta

Unit: number

Rollup Type: summation

Collection Level: 3

VC/ESX: Yes/Yes

ο

ο

numberWrite

Disk Write Requests

VM

Number of times data was written to each virtual disk on the virtual machine.

Host

Number of times data was written to each LUN on the host during the collection interval.

Stats Type: delta

Unit: number

Rollup Type: summation

Collection Level: 3

VC/ESX: Yes/Yes

ο

ο

queueLatency

Queue Command Latency

Average amount of time spent in the VMkernel queue, per SCSI command, during the collection interval.

Stats Type: absolute

Unit: millisecond

Rollup Type: average

Collection Level: 2

VC/ESX: Yes/Yes

o

ο

ο

queueReadLatency

Queue Read Latency

Average amount of time taken during the collection interval per SCSI read command in the VMKernel queue.

Stats Type: absolute

Unit: millisecond

Rollup Type: average

Collection Level: 2

VC/ESX: Yes/Yes

o

ο

ο

queueWriteLatency

Queue Write Latency

Average amount time taken during the collection interval per SCSI write command in the VMKernel queue.

Stats Type: absolute

Unit: millisecond

Rollup Type: average

Collection Level: 2

VC/ESX: Yes/Yes

o

ο

ο

read

Disk Read Rate

VM

Rate at which data is read from each virtual disk on the virtual machine.

Host

Rate at which data is read from each LUN on the host.

read rate = # blocksRead per second × blockSize

Stats Type: rate

Unit: kiloBytesPerSecond

Rollup Type: average

Collection Level: 2

VC/ESX: Yes/Yes

ο

ο

totalLatency

Disk Command Latency

Average amount of time taken during the collection interval to process a SCSI command issued by the Guest OS to the virtual machine. The sum of kernelLatency and deviceLatency.

Stats Type: absolute

Unit: millisecond

Collection Level: 2

Rollup Type: average

VC/ESX: Yes/Yes

o

ο

ο

totalReadLatency

Disk Read Latency

Average amount of time taken during the collection interval to process a SCSI read command issued from the Guest OS to the virtual machine. The sum of kernelReadLatency and deviceReadLatency.

Stats Type: absolute

Unit: millisecond

Collection Level: 2

Rollup Type: average

VC/ESX: Yes/Yes

o

ο

ο

totalWriteLatency

Disk Write Latency

Average amount of time taken during the collection interval to process a SCSI write command issued by the Guest OS to the virtual machine. The sum of kernelWriteLatency and deviceWriteLatency.

Stats Type: absolute

Unit: millisecond

Collection Level: 2

Rollup Type: average

VC/ESX: Yes/Yes

o

ο

ο

usage

Disk Usage

Aggregated disk I/O rate. For hosts, this metric includes the rates for all virtual machines running on the host during the collection interval.

Stats Type: rate

Unit: kiloBytesPerSecond

Collection Level: 1(4)

Rollup Type: average (min/max)

VC/ESX: Yes/Yes

ο

ο

write

Disk Write Rate

VM

Rate at which data is written to each virtual disk on the virtual machine.

Host

Rate at which data is written to each LUN on the host.

Write rate = blocksWritten/second * blockSize

Stats Type: rate

Unit: kiloBytesPerSecond

Collection Level: 2

Rollup Type: average

VC/ESX: Yes/Yes

ο

ο