Use cases

This section describes the following Dell EMC Unity monitoring use cases:

  • Storage Capacity Monitoring and Optimization
  • Performance Optimization
  • Traffic Management

Storage Capacity Monitoring and Optimization

Making sure that a storage system has enough remaining disk space available is critical for several reasons:

  • SAN administrators want to make sure to be able to provision disk space for new servers when requested, as quickly as possible.
  • The storage system itself may need additional disk space for specific features to work properly, like automatic snapshots, mirroring, etc.
  • If thin provisioning is used, the remaining disk space becomes dramatically critical since the inability to allocate additional space to a LUN when requested by the subscriber host will lead to catastrophic data loss and corruption.

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.

To verify the available disk space in several storage pools:

  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 inline
  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

    Adding a Dashlet

  7. Select Configure Dashlet by clicking the inline button

    Adding a Dashboard

  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 storage pools

    Selecting the Dell EMC Unity Storage Device

  10. Select the Consumed Capacity Percentage parameter for the first storage pool, and click Apply

    Selecting the Consumed Capacity Percentage Parameter

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

  12. The dashboard is completed and shows the Consumed Capacity Percentage for the selected storage pool(s).

    <strong>Consumed Capacity Percentage</strong> for the Selected Dell EMC Unity Storage Pool

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

Identifying Unmapped (Orphans) Volumes

Over time, as servers connected to a SAN get decommissioned, administrators find an increasing number of unmapped LUNs, or volumes that are no longer used by any server. These LUNs, while unused, still occupy disk space in the storage system. Being able to identify such unmapped LUNs and reclaim the disk space uselessly consumed by these LUNs will help administrators avoid unnecessary upgrades and extensions of their storage systems.

To know which volumes are not mapped to any server and therefore safe to remove, you will have to schedule the LUNs Mapping Table report as described below:

  1. Edit your Dell EMC Unity monitoring policy:

    Editing the 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 inline 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 inline to access the monitoring options panel.
  2. Locate the Reporting section:

    Scheduling the LUNs Mapping Table Report

  3. In the Schedule section, indicate the time at which the LUNs Mapping Table report must be generated

  4. Check the LUNs Mapping Table box. The .csv file generated for this report consists in the following comma-separated data: Storage System, Hostname, Host WWN/IQN, LUN, Fiber Ports or Size
  5. Click OK
  6. Click Save. The generated file is time-stamped and stored in %PATROL_HOME%\log.
  7. Open the csv file in Excel and only display the Not Mapped volumes:

    Identifying the Unmapped Volumes

Identifying Unused Volumes

When a server is decommissioned or reconfigured, its associated LUNs can stay mapped preventing storage administrator from accurately identifying unused LUNs. Since the Dell EMC Unity KM for PATROL monitors permanently the traffic on each LUN, it becomes easy to detect LUNs for which the activity is null.

  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 inline
  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 - Top/Bottom Performers template, and then click Close

    Adding a Dashlet

  7. Select Configure Dashlet by clicking the inline button

    Adding a Dashboard

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

    Selecting the Unity Volume Monitor Type

  9. Configure the graph parameters:

  • In the Type field, select Top N Graph,
  • In the Number of Bars field, select the number of volumes for which you need to compare activity (default is 10)
  1. Set the Refresh Rate.
  2. Select the Time Since Last Activity parameter, and click Apply.

    Selecting the Time Since Last Activity Parameter

  3. Click Save.

  4. The dashboard is completed and shows the top x volumes with the higher number of days of inactivity. Pass the mouse over a bar to view the average, high and low values for a volume.

    Viewing the Top X Volumes with the Higher Number of Days of Inactivity

Performance Optimization

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 inline
  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

    Adding a Dashlet

  7. Select Configure Dashlet by clicking the inline button

    Adding a Dashboard

  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

    Selecting the Dell EMC Unity Storage Device

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

    Selecting the Read Byte Rate and Write Byte Rate Parameters

  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

    <strong>Read Byte Rate</strong> and <strong>Write Byte Rate</strong> Parameters for the Selected Dell EMC Unity 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 inline
  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 inline button

    Adding a Dashboard

  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

    Selecting the Dell EMC Unity Storage Device

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

    Selecting the Processor Utilization Parameter

  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

    Processor Utilization for the selected Dell EMC Unity 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:

Response Time performance
Less than 10 ms Very good
Between 10 – 20 ms OK
Between 20 – 50 ms Slow, needs attention
Greater than 50 ms I/O bottleneck

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 inline
  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

    Adding a Dashlet

  7. Select Configure Dashlet by clicking the inline button

    Adding a Dashboard

  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

    Selecting the Dell EMC Unity Storage Device

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

    Selecting the Dell EMC Unity Volume

  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.

Traffic Management

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 inline
  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

    Adding a Dashlet

  7. Select Configure Dashlet by clicking the inline button

    Adding a Dashboard

  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

    Selecting the Unity Volume Monitor Type

  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

    Selecting the Read Byte Rate and Write Byte Parameters

  12. Click Save.

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

    Selecting the Time Since Last Activity Parameter

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:

    Editing the 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 inline 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 inline to access the monitoring options panel.
  2. Locate the Reporting section:

    Scheduling Reports

  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.