Disk Activity - VM Test
This test reports statistics pertaining to the input/output utilization of each physical disk on a VM.
Target of the test : A Nutanix Acropolis server
Agent deploying the test : A remote agent
Outputs of the test : One set of results for every combination of virtual_guest:disk_partition or guest_user:disk_partition.
Configurable parameters for the test
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Measurements made by the test
Measurement | Description | Measurement Unit | Interpretation |
---|---|---|---|
Percent virtual disk busy: |
Indicates the percentage of elapsed time during which the disk is busy processing requests (i.e., reads or writes). |
Percent |
Comparing the percentage of time that the different disks are busy, an administrator can determine whether load is properly balanced across the different disks. |
Percent reads from virtual disk: |
Indicates the percentage of elapsed time that the selected disk drive is busy servicing read requests. |
Percent |
|
Percent writes to virtual disk: |
Indicates the percentage of elapsed time that the selected disk drive is busy servicing write requests. |
Percent |
|
Virtual disk read time: |
Indicates the average time in seconds of a read of data from the disk. |
Secs |
|
Virtual disk write time: |
Indicates the average time in seconds of a write of data from the disk. |
Secs |
|
Avg. queue for virtual disk: |
Indicates the average number of both read and write requests that were queued for the selected disk during the sample interval. |
Number |
|
Current queue for virtual disk: |
The number of requests outstanding on the disk at the time the performance data is collected. |
Number |
This measure includes requests in service at the time of the snapshot. This is an instantaneous length, not an average over the time interval. Multi-spindle 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. |
Reads from virtual disk: |
Indicates the number of reads happening on a logical disk per second. |
Reads/Sec |
A dramatic increase in this value may be indicative of an I/O bottleneck on the guest. |
Data reads from virtual disk: |
Indicates the rate at which bytes are transferred from the disk during read operations. |
KB/Sec |
A very high value indicates an I/O bottleneck on the guest. |
Writes to virtual disk: |
Indicates the number of writes happening on a local disk per second. |
Writes/Sec |
A dramatic increase in this value may be indicative of an I/O bottleneck on the guest. |
Data writes to virtual disk: |
Indicates the rate at which bytes are transferred from the disk during write operations. |
KB/Sec |
A very high value indicates an I/O bottleneck on the guest. |
Disk service time: |
Indicates the average time that this disk took to service each transfer request ( i.e., the average I/O operation time) |
Secs |
A sudden rise in the value of this measure can be attributed to a large amount of information being input or output. A consistent increase however, could indicate an I/O processing bottleneck. |
Disk queue time: |
Indicates the average time that transfer requests waited idly on queue for this disk. |
Secs |
Ideally, the value of this measure should be low. |
Disk I/O time: |
Indicates the average time taken for read and write operations of this disk. |
Secs |
The value of this measure is the sum of the values of the Disk service time and Disk queue time measures. A consistent increase in the value of this measure could indicate a latency in I/O processing. |
The detailed diagnosis of the Percent virtual disk busy measure, if enabled, provides information such as the Process IDs executing on the disk, the Process names, the rate at which I/O read and write requests were issued by each of the processes, and the rate at which data was read from and written into the disk by each of the processes. In the event of excessive disk activity, the details provided in the detailed diagnosis page will enable users to figure out which process is performing the I/O operation that is keeping the disk busy. The detailed diagnosis for this test is available for Windows guests only, and not Linux guests.
Figure 1 : The detailed diagnosis of the Percent virtual busy measure