MDisk Groups - VDisk Workload Activity report

Use this report to monitor the performance of virtual disks (VDisks) in managed disk (MDisk) groups. The workload activity of each MDisk group is determined by calculating the average and the maximum peak utilization of the VDisks in the MDisk group.

Restriction: This report applies only to SAN Volume Controller and Storwize systems.

Reporting period

The name of the storage virtualizer, the date filter such as Last 7 days, and the reporting period are displayed in the report.

Retention of report data

If you remove an MDisk group or a VDisk, the daily data that is collected for reports is retained for a configurable period. The default is 90 days. If you run a report after the data retention period expired, the daily data for the MDisk group or the VDisk is unavailable.

VDisk migration

If a VDisk is migrated to another MDisk group during a reporting period, daily VDisk reports are produced only for the target MDisk group. For the target MDisk group, VDisk reports are produced from the day that the VDisk is migrated from the source MDisk group until the last day of the reporting period.

Charts

The maximum length of an MDisk group, VDisk, or storage resource group name in charts is 25 characters. Names that are longer than 25 characters are truncated. To indicate that a name is truncated, an ellipsis (...) is appended to the name. For example, if the name of an MDisk group is myverylongmanageddiskgroupname123 in a chart, it is truncated and displayed as myverylongmanageddiskgroupname...

Two charts are shown:

Most Active MDisk Groups chart

For each MDisk group two bars are shown:

A yellow bar that shows average VDisk utilization
A red bar that shows maximum VDisk utilization

To calculate average VDisk utilization, the following formula is used:

average(vdisk_peak_utilization)

To calculate maximum VDisk utilization, the following formula is used:

maximum(vdisk_peak_utilization)

In this sample excerpt of report output for VDisk1, the values that are required to calculate average and maximum VDisk utilization are provided.

VDisk Report Date	VDisk Peak Utilization (%)
Dec 6 2011	86.30
Dec 7 2011	50.01
Dec 8 2011	79.41

To calculate the average value of a VDisk:

The values for VDisk1 in the VDisk Utilization (%) column are added:
```
86.30 + 50.01 + 79.41 = 215.72 
```
The total is divided by the number of days that are specified in the date range. For example, if the reporting period spans 3 days, the total is divided by 3.
```
215.72 ÷ 3 = 71.91
```

In the sample, the average peak VDisk utilization is 71.91.

For each MDisk group, the maximum VDisk utilization is also shown in the chart. The maximum VDisk utilization is the highest value for a VDisk in the VDisk Utilization (%) column. In the sample, the highest value for VDisk1 is 86.30.

Least Active MDisk Groups chart

For each MDisk group two bars are shown:

A yellow bar that shows average VDisk utilization
A red bar that shows maximum VDisk utilization

The same formulas that are used in the most active MDisk group chart are also used in the least active MDisk group chart.

The number of MDisk groups in the storage virtualizer determines how many MDisk groups are shown in each chart, as shown in the following table.

Number of MDisk groups in the storage virtualizer	Number of MDisk groups in the Most Active MDisk Groups chart	Number of MDisk groups in the Least Active MDisk Groups chart
≥ 10	5	5
9	5	4
8	4	4
7	4	3
6	3	3
5	3	2
4	2	2
3	2	1
2	1	1
1	1	0

Tip: Click the bar that represents an MDisk group in a chart to open the MDisk Group - VDisk Workload Activity Details Report. Alternatively, click the name of the MDisk group in the report. Click the name of the VDisk in the report to open the VDisk Details Report.

Threshold values

The names of the threshold values that are used in the report to monitor workload activity for VDisks are as follows:

VDisk Max Read Response Time Threshold
VDisk Max Write Response Time Threshold
Max Read Cache Hits Time Threshold
Max Read I/O Rate Threshold
Max Write I/O Rate Threshold

Threshold values are set during installation. If a threshold value is changed during a reporting period, the original value and the new threshold value are displayed as minimum and maximum values. If, for example, the VDisk maximum read response time threshold value is changed during a reporting period from 70% to 80%, the name of the column is changed to VDisk Max Read Response Time Threshold of {70 - 80%} Exceeded By (hr.:min.). The convention that is used to represent a threshold value is a number followed by the percent sign and enclosed in brackets: {%}. When the report is run, the variable value is replaced with the threshold value. To calculate whether read or write response time thresholds are exceeded, the following formula is used: (maximum_response_time_value × maximum_response_time_threshold value)/100. The result is converted from seconds to hours and minutes, and displayed in the report. Read and write response times are sampled at 5-minute intervals over a 24-hour period.

Report output

For each VDisk in an MDisk group, the following information is provided:

MDisk Group: The name of the MDisk group.

VDisk: The name of the VDisk.

VDisk Report Date: The date that the data was collected for the report.

VDisk Capacity (GB): The total storage capacity of the VDisk in GB.

VDisk Thin Provisioning Capacity Status: The warning level threshold is set in the thin provisioning profile for the VDisk. The threshold is exceeded when the capacity of the VDisk that is used exceeds or is equal to the warning level threshold. If the used capacity of the VDisk in GB is ≥ the specified warning threshold value, a status value of Warning is displayed. If the used capacity of the VDisk in GB is < the specified warning threshold value, a status value of OK is displayed. If thin provisioning is not used, a status value of Not Applicable is displayed.

VDisk Peak Utilization (%): The highest value of VDisk utilization over a 24-hour period.

VDisk Read I/O Rate (ops/s): The read I/O rate of the VDisk in operations per second.

VDisk Max Read I/O Rate (ops/s): The maximum read I/O rate of the VDisk in operations per second.

VDisk Average Read Response Time (ms/op): The average read response time in milliseconds per operation.

VDisk Max Read Response Time (ms/op): The maximum read response time in milliseconds per operation.

VDisk Max Read Response Time Threshold of {%} Exceeded By (hr.:min.): The number of hours and minutes that the maximum read response time threshold for the VDisk is exceeded over a 24 hour period.

VDisk Write I/O Rate (ops/s): The write I/O rate in operations per second.

VDisk Average Write Response Time (ms/op): The average write response time in milliseconds per operation.

VDisk Max Write Response Time (ms/op): The maximum write response time in milliseconds per operation.

VDisk Max Write Response Time Threshold of {%} Exceeded By (hr.:min.): The number of hours and minutes that the maximum write response time threshold for the VDisk is exceeded over a 24 hour period.

VDisk Max Read Density Rate (ops/s per GB): The maximum read density rate in operations per second per GB. This value is calculated by dividing the maximum read I/O rate in operations per second by the number of GB that the VDisk was allocated.

VDisk I/O Rate Share of Total VDisk Read I/O Rate (%): The maximum read I/O rate of the VDisk as a percentage of the total maximum read I/O rate of all the VDisks in the MDisk group.

VDisk Capacity Share of Total VDisk Capacity (%): The real capacity of the VDisk as a percentage of the real capacity of all the VDisks in the MDisk group.

VDisk Average Read Cache Hits (%): The average read cache hits in percent.

VDisk Max Read Cache Hits (%): The maximum read cache hits in percent.

VDisk Max Read Cache Hits Time Threshold of {%} Exceeded By (hr.:min.): The number of hours and minutes that the maximum read cache hits time threshold is exceeded over a 24 hour period.

VDisk Max Read I/O Rate Threshold of {%} Exceeded By (hr.:min.): The number of hours and minutes that the maximum read I/O rate threshold is exceeded over a 24 hour period.

VDisk Max Write I/O Rate Threshold of {%} Exceeded By (hr.:min.): The number of hours and minutes that the maximum write I/O rate threshold is exceeded over a 24 hour period.

VDisk Max Write Cache Delay I/O Rate (ops/s): The maximum write cache delay I/O rate of the VDisk in operations per second.