eG Monitoring
 

Measures reported by WVDDiskActivityTest

This test reports statistics pertaining to the input/output utilization of each physical disk on the chosen User/Desktop.

Outputs of the test : One set of results for each disk partition supported by the chosen User/Desktop.

The measures made by this test are as follows:

Measurement Description Measurement Unit Interpretation
Percent_busy Indicates the percentage of elapsed time during which this disk was 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 the application load is properly balanced across the different disks.

The detailed diagnosis of this measure will reveal the top-10 I/O-intensive applications/processes executing on the virtual desktop. If the Trace parameter of the test is set to Yes, then the detailed diagnostics will additionally display I/O usage metrics per file stored in the disk partition. The files included in the detailed diagnosis will be the ones that fulfill the following criteria:

  • The files involved in the disk events captured during the interval specified against Event Capture Interval in Secs;
  • The size of the data read from/written to the files is greater than or equal to the values specified against Read Size in KB and Write Size in KB.

    (OR)

    The responsiveness of the files to I/O requests is greater than or equal to the value specified against the Disk Response Time Secs parameter.
Percent_disk_reads Indicates the percentage of elapsed time that the selected disk drive is busy servicing read requests. Percent  
Percent_disk_writes Indicates the percentage of elapsed time that the selected disk drive is busy servicing write requests. Percent  
Disk_read_time Indicates the average time in seconds of a read of data from the disk. Secs  
Disk_write_time Indicates the average time in seconds of a write of data from the disk. Secs  
Avg_queue_length Indicates the average number of both read and write requests that were queued for the selected disk during the sample interval. Number Using the detailed diagnosis of this measure, you can isolate the exact application and process on the virtual desktop that has the highest level of read/write activity.
Current_queue_length 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.
Read_rate 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 server.
Data_read_rate 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 server.
Write_rate 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 server.
Data_write_rate 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 server.
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.
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.
Avg_io_read_size Indicates the average number of bytes transferred from disk during read operations. KB Larger I/Os tend to have higher latency (for example, BACKUP/RESTORE operations issue 1 MB transfers by default).
Avg_io_write_size Indicates the average number of bytes transferred into disk during write operations. KB
Split_io Reports the rate at which the operating system divides I/O requests to the disk into multiple requests. Splits/Sec A split I/O request might occur if the program requests data in a size that is too large to fit into a single request or if the disk is fragmented. Factors that influence the size of an I/O request can include application design, the file system, or drivers. A high rate of split I/O might not, in itself, represent a problem. However, on single-disk systems, a high rate for this counter tends to indicate disk fragmentation.