Use cases

Reporting on Disk Space Consumption

The Unity Storage System Monitor reports various metrics regarding the disk space in the storage system:

• The total subscribed capacity, i.e. the total amount of disk space exposed to the servers with the Subscribed Capacity attribute
• The total amount of free disk space with the Available Capacity attribute.

For a more granular view of the disk space usage in the disk array, analyze the attributes of the Unity Storage Pool Monitor:

• The Subscribed Capacity attribute of the Unity Storage Pool Monitor represents the amount of disk space that has been made available to the subscriber hosts, or in other words, the amount of disk space that is seen by the servers connected to the storage system.
• The Consumed Capacity attribute of the Unity Storage Pool Monitor represents the actual space usage in the storage pool. For “thin” pools (when thin provisioning is enabled on the storage system), this value is normally lower than the Subscribed Capacity, as it is the main purpose of thin provisioning. For traditional pools, the Consumed Capacity attribute has the same value as the Subscribed Capacity attribute, as the entirety of the subscribed disk space is fully allocated in the storage pool.
• The Consumed Capacity Percentage attribute is the most critical one, even for non-thin storage pools, as a storage pool usage nearing 100% means that SAN administrators will not be able to create new LUNs in the storage pool. By default, no alarm or warning threshold is set on this parameter as the fullness of a storage pool may be a normal situation.

Detecting Oversubscription Situations (Thin Provisioning)

We call an oversubscription situation when:

• The storage pool is configured for thin provisioning (“thin storage pool”)
• The storage pool is oversubscribed, i.e. the total disk space visible to the hosts (subscribers) is greater than its actual capacity (this situation is normal for a thin pool since it is its very purpose)
• The storage pool actual consumed capacity is higher than 75%.

Such situation is highly critical because the inability to allocate additional space to a LUN when requested by the subscriber host will lead to catastrophic data loss and corruption.

The Oversubscription Situation attribute will alert you to an oversubscription situation by triggering an alarm. When such an alarm is issued by the KM, it is highly recommended that the SAN administrators add capacity to the storage pool as soon as possible.

Reclaiming Space of Unused Volumes

Diagnosing a Bad Physical Disk Layout

A non-optimal physical disk layout can cause one single physical disk to become the bottleneck of a SAN. To verify that the amount of data being read/written on a physical disk is well-balanced over time across all physical disks, you need to compare the throughput of read/write data for each physical disk in your Dell EMC Unity storage systems.

To compare the I/Os of physical disks, you will need to create a dashboard. Dashboards allow you to gather specific types of data and display them in a consolidated graphical format. For detailed information about dashboards options and features, refer to the BMC documentation.

1. Log on to the TrueSight console
2. Select Dashboards from the navigation pane
3. In the Dashboards page, click Add Dashboard or select Add Dashboard from the dashboard action menu
4. Enter a Title for your dashboard and configure a Global Filter, if needed
5. Click Add Dashlet to open the dashlet library for the first column of the row
6. From the dashlet library, select the Device Performance template, and then click Close

   

7. Select Configure Dashlet by clicking the button

   

8. In the panel of input fields and options that opens below the dashboard, enter a Title for the dashlet and specify a Refresh Rate (default is 5 minutes)

9. Select the Dell EMC Unity storage device for which you need to compare physical disks I/Os

   

10. Select the Read Byte Rate and Write Byte Rate parameters for the first physical disk, and click Apply

    

11. Repeat this operation in the next column(s) of the dashboard with other physical disks and click Save

12. The dashboard is completed and shows the Read Byte Rate and Write Byte Rate parameters for the selected physical disks

    

13. Verify that the Read Byte Rate and Write Byte Rate parameters of all the physical disks have similar average values to ensure that I/Os are well-balanced across all physical disks.

Detecting High Processor Utilization

Detecting a high processor utilization is crucial to prevent controllers to overload and cause critical performance degradations. To detect high processor utilization, you need to compare the actual processor utilization and the overall device throughput to determine which controller may constitute a bottleneck.

To compare the utilization of processors, you will need to create a dashboard. Dashboards allow you to gather specific types of data and display them in a consolidated graphical format. For detailed information about dashboards options and features, refer to the BMC documentation.

To detect high processor utilization:

1. Log on to the TrueSight console
2. Select Dashboards from the navigation pane
3. In the Dashboards page, click Add Dashboard or select Add Dashboard from the dashboard action menu
4. Enter a Title for your dashboard and configure a Global Filter, if needed
5. Click Add Dashlet to open the dashlet library for the first column of the row
6. From the dashlet library, select the Device Performance template, and then click Close
7. Select Configure Dashlet by clicking the button

   

8. In the panel of input fields and options that opens below the dashboard, enter a Title for the dashlet and specify a Refresh Rate (default is 5 minutes)

9. Select the Dell EMC Unity storage device for which you need to compare the processor utilization of the controllers

   

10. Select the Processor Utilization parameter for the first controller, and click Apply

    

11. Repeat this operation in the next column(s) of the dashboard with other controllers and click Save

12. The dashboard is completed and shows the Processor Utilization for the controllers

    

Make sure that the Processor Utilization is lower than 80%. A processor utilization over 80% highlights a potential overloaded situation and indicates that the controller may constitute a bottleneck for the storage system.

Diagnosing Slow Volumes

When servers are experiencing slow I/Os performance, you may want to verify the actual response time of the volumes the server is relying on. The response time represents the average time it takes to complete the read/write operations on a volume during the collection interval. Typically, the average response time is below 10 milliseconds. You may also want to compare this value with other volumes response time to find out if they have relatively similar throughput or if one server is really getting worse I/O performance than another.

The industry common guidelines in terms of response time are:

To identify slow volumes, you will need to create a simple dashboard. Dashboards allow you to gather specific types of data and display them in a consolidated graphical format. For detailed information about dashboards options and features, refer to the BMC documentation.

To diagnose slow volumes:

1. Log on to the TrueSight console
2. Select Dashboards from the navigation pane
3. In the Dashboards page, click Add Dashboard or select Add Dashboard from the dashboard action menu
4. Enter a Title for your dashboard and configure a Global Filter, if needed
5. Click Add Dashlet to open the dashlet library for the first column of the row
6. From the dashlet library, select the Device Performance template, and then click Close

   

7. Select Configure Dashlet by clicking the button

   

8. In the panel of input fields and options that opens below the dashboard, enter a Title for the dashlet and specify a Refresh Rate (default is 5 minutes)

9. Select the Dell EMC Unity storage device for which you need to compare volumes response times

   

10. Select the Response Time parameter for the first volume, and click Apply

    

11. Repeat this operation in the next columns of the dashboard for other volumes and click Save

12. The dashboard is completed and shows the Response Time for all the selected volumes

If the response time is high, you will need to check the amount of data that is written and read on this volume. The bad performance may simply be due to an abnormally large amount of data to process.

Identifying Busiest Volumes

To identify the volumes that generate the most traffic on the disk array, you can use the Read Byte Rate and Write Byte Rate parameters of the Unity Volume Monitor.

1. Log on to the TrueSight console
2. Select Dashboards from the navigation pane
3. In the Dashboards page, click Add Dashboard or select Add Dashboard from the dashboard action menu
4. Enter a Title for your dashboard and configure a Global Filter, if needed
5. Click Add Dashlet to open the dashlet library for the first column of the row
6. From the dashlet library, select the Monitors - Performance Overview template, and then click Close

   

7. Select Configure Dashlet by clicking the button

   

8. From the Focus list, select Multimetric comparison

9. Select the Monitor Type for which you want to create a graph. In our example, Unity Volume

   

10. Select the Volumes Monitors to be displayed in the graph and click Done

11. For each selected volume, check the Read Byte Rate and Write Byte Rate parameters and click Apply

    

12. Click Save.

13. The dashboard is completed and shows the busiest volumes.

    

Generating Activity Reports

Dell EMC Unity KM for PATROL can automatically produce text reports that provide detailed and valuable information about your monitored storage systems.

To schedule the generation of activity reports:

1. Edit your Dell EMC Unity monitoring policy:

   

   • Log on to the TrueSight console.
   • In the navigation pane, expand Configuration and select Infrastructure Policies.
   • In the Infrastructure Policies page, locate the monitoring policy you wish to modify, click its action button and click Edit.
   • In the Edit Monitoring Policy page, locate the Dell EMC Unity Storage Configuration you wish to modify and click its action button to access the monitoring options panel.

2. Locate the Reporting section:

   

3. In the Schedule section, indicate the time at which the report(s) must be generated

4. Check the Activity report type to automatically generate the following reports:
   • Storage pools: Reports on Transfer, Read and Writes Bytes for all monitored storage pools
   • Volumes: Reports on Transfer, Read and Writes Bytes for all monitored volumes
   • Physical disks: Reports on Transfer, Read and Writes Bytes for all monitored physical disks
   • FC Ports: Reports on Transfer Bytes for all monitored ports.

5. Click OK

6. Click Save.

The generated file(s) are time-stamped and stored in %PATROL_HOME%\log for the specific time set through the History Retention Period parameter.