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# Modify storage groups

Storage groups are a collection of devices that are stored on the storage system, and an application, a server, or a collection of servers use them.

## About this task

This procedure explains how to modify storage groups on storage systems running HYPERMAX OS 5977 or PowerMaxOS 5978.

Before you begin:

- You must be an Administrator or StorageAdmin.
- The maximum number of storage groups that are allowed on a storage system is 16,384.
- A storage group can contain up to 4,096 storage volumes.
- A volume can belong to more than one storage group.
- A volume can belong to multiple storage groups when only one of the groups has an SRP.

To modify a storage group:

## Steps

1. Select the storage system.
2. Select STORAGE > Storage Groups.
3. Select the storage group and click Modify to open the Modify Storage Group dialog box.
4. Do any number of the following:
   1. Change the Storage Group Name by selecting it and typing a new name over it. Storage group names must be unique from other storage groups on the storage system and cannot exceed 64 characters. Only alphanumeric characters, underscores ( _ ), and dashes (-) are allowed. Storage group names are case-insensitive.

      Note the following about renaming storage groups:

      - If renaming a storage group with a workload, you have to wait some time before the workload is visible in the Details view of the storage group.
      - If renaming a storage group configured compliance alerts, the compliance alerts must be deleted manually. For instructions, see Delete compliance alerts policies.
   2. Change the Storage Resource Pool by selecting the new pool from the drop-down menu. Setting this property to None creates the storage group without an SRP. External storage resource pools are listed below the External heading.
   3. Change the Service Level for the storage group. Service levels specify the characteristics of the provisioned storage, including maximum response time, workload type, and priority. This field defaults to None if you set the Storage Resource Pool to None. Possible values are:

      Service level | Performance type | Use case
      --- | --- | ---
      Diamond (Default) | Ultra high | HPC, latency sensitive
      Platinum | Very high | Mission critical, high rate OLTP
      Gold | High | Very heavy I/O, database logs, datasets
      Silver | Price/Performance | Database datasets, virtual applications
      Bronze | Cost optimized | Backup, archive, file
      Optimized |  | Places the most active data on the highest performing storage and the least active on the most cost-effective storage.

   4. Change the Workload Type assigned to the service level.

      | NOTE: Workloads are supported on storage systems running HYPERMAX OS 5977.

   5. Add or remove Volumes.
   6. Do the following to change the capacity of the storage group, depending on whether the group contains volumes of the same capacity or mixed capacities:
      - If the group contains volumes of the same capacity, do one of the following:
        - Type or select an increased number of volumes in the Volumes drop-down menu.

          | NOTE: A yellow warning triangle is displayed if you attempt to add one or more volumes to an SRDF protected storage group without pairing the new volume with the remote storage group. This results in an unprotected and unmanageable SRDF storage group. Double-click the yellow triangle to display a dialog enabling you to add SRDF pairs to a remote storage group (see Add SRDF pairs to a remote storage group).

          | NOTE: You can expand devices that are part of the SRDF/Metro high availability relationship without any service interruption.

        - Type or select an increased unit capacity of the volumes and/or change the unit in the Volume Capacity drop-down menus.

          | NOTE: In mixed FBA/CKD All Flash systems, volume capacity defaults to GB for FBA Storage Groups and Cyl for CKD Storage Groups.

      - If the group contains volumes of mixed capacities, click Edit custom capacity to open the Modify Custom Capacity dialog box. Change the number of Volumes by capacity, and click OK. You can only use the Allocate capacity for each volume option for newly created volumes, not existing volumes.

      The Total Capacity and Additional Capacity figures are updated to reflect any changes.

      | NOTE: The maximum volume size that is supported on a storage system running HYPERMAX OS 5977 is 64 TB. All Flash systems running the HYPERMAX OS 5977 Q2 2017 Service Release or later supports a maximum CKD device size of up to 1,182,006 cylinders.

   7. SRDF storage group volume capacity can be expanded using the controls. For SRDF Storage Groups, you specify an SRDF group number so that the dialog enabling you to expand remote volumes can also be displayed (see Expand remote volumes).
   8. Optional: Add one or more storage groups by hovering over the area to the right of the volume capacity and selecting .
   9. Optional: Create a storage group with multiple volume sizes or edit the storage group by hovering over the area to the right of the volume capacity and selecting (see Edit storage group volume details).
   10. Optional: To add a child storage group, do one of the following:
       - On all-flash storage systems, click Add Storage Group.
       - On all other storage systems, click Add Service Level.
       - Modify any of the service level parameters, as previously described.
5. Select the blue text next to Snapshot Policies to associate up to four snapshot policies with a storage group and click OK.
6. Data reduction is enabled by default on All Flash systems running the HYPERMAX OS 5977 Q3 2016 Service Release or later. To disable it, clear the Enable Data Reduction check box. In a cascaded setup, changes are passed to each of the child storage groups. For more information about data reduction, see Understanding data reduction.
7. Optional: When expanding a storage group for file, click Set Dynamic LUNs to modify dynamic LUN addresses.
8. Changing the Storage Resource Pool value from None to an SRP instance enables the Run Performance Impact button. Click Run Performance Impact to view the performance impact of the SRP change (see Performance Impact).
9. Do one of the following:
   - Click Run Now to perform the operation now.
   - Expand Run Now and click Add to Job List to add this task to the job list, from which you can schedule or run the task at your convenience. For more information, see Schedule jobs and Preview jobs.
   If the storage group is a SRDF/Metro storage group with an existing SRDF group, clicking Run Now results in the display of the Expand Remote Volumes dialog (see Expand remote volumes).