Creating data reduction pools

To use data reduction technologies on the system, you need to create a data reduction pool, create volumes with the data reduction pool, and map these volumes to hosts that support SCSI unmap commands.

Data reduction is a set of techniques that can be used to reduce the amount of usable capacity that is required to store data. An example of data reduction includes data deduplication. Data reduction can increase storage efficiency and performance and reduce storage costs, especially for flash storage. Data reduction reduces the amount of data that is stored on external storage systems and internal drives by reclaiming previously used capacity that are no longer needed by host systems. To estimate potential capacity savings that data reduction can provide on the system, use the Data Reduction Estimation Tool (DRET). This tool analyzes existing user workloads that are being migrated to a new system. The tool scans target workloads on all attached storage arrays, consolidates these results, and generates an estimate of potential data reduction savings for the entire system.

For more information about DRET, see https://www.ibm.com/support/pages/node/6217841. For more information about Comprestimator, see https://www.ibm.com/support/pages/node/6209688.

The system supports data reduction pools which can use different capacity savings methods simultaneously, increasing the capacity savings across the entire pool. Data reduction pools also support deduplication. When deduplication is specified for a volume, duplicate versions of data are eliminated and not written to storage, thus saving more usable capacity. Some models or software versions require specific hardware or software to use this function.

Support for the host SCSI unmap command is enabled by default.

Using the management GUI

To create data reduction on the system, complete these steps:
  1. Create a data reduction pool by completing these steps:
    1. In the management GUI, select Pools > Pools.
    2. On the Pools page, click Create.
    3. On the Create Pool page, enter a name of the pool and select Data Reduction.
    4. Click Create.
  2. Add storage to the data reduction pool by completing these steps:
    1. In the management GUI, select Pools > Pools.
    2. Right-click the data reduction pool that you created and select Add Storage.
    3. Select from the available storage and reserve capacity to the pool. Click Assign.
      Note: You cannot select from available storage when you are creating a data reduction child pool. A data reduction child pool has access to the complete available capacity of the parent pool without limit. A data reduction child pool cannot be created if the parent pool does not have available capacity.
  3. Create volumes that use supported capacity savings methods in the data reduction pool and map them to hosts by completing these steps:
    1. In the management GUI, select Volumes > Volumes.
    2. On the Volumes page, click Create Volumes.
    3. On the Create Volume page, select the type of volume that you want to create.
    4. Enter the following information for the volume:
      Pool
      Select a data reduction pool from the list.
      Volume details
      Enter the quantity, capacity, and name for the volume or volumes that you are creating.
      Capacity savings
      Select one of the supported capacity savings methods. For any of these supported options, you can also select to use deduplication for the volume that you create. For example, you can create a thin-provisioned volume that also uses deduplication to remove duplicate data.
      Note: If your system contains self-compressed drives, ensure that volumes in data reduction pools are created with compression enabled or with no data savings. If data reduction pools are created as thin-provisioned volumes without compression, the system cannot calculate accurate usable capacity.
    5. Click Create and Map.
      Note: Select Create to create the volumes in the data reduction pool without mapping to hosts. If you want to map volumes to hosts later, select Hosts > Hosts > Add Hosts.
    6. On the Create Mapping page, select Host to display all hosts that are available for mapping. Hosts must support SCSI unmap commands. Verify that the selected host type supports SCSI unmap commands. Click Next.
    7. Verify the volume, and then click Map Volumes.

Using the command-line interface

To create a data reduction pool on the system, complete these steps:
  1. To create a data reduction pool, enter the following command:
    mkmdiskgrp -name pool_name -ext extent_size -datareduction yes
    where pool_name is the name of the pool and extent_size is the extent size of the pool.
  2. To create a child data reduction pool, enter the following command:
    mkmdiskgrp -parentmdiskgrp data_reduction_parent_pool -datareduction yes -noquota
    where data_reduction_parent_pool is the name of the parent data reduction pool.
  3. To create a compressed volume that has deduplication enabled in a data reduction pool, enter the following command: 
    mkvolume -name name -pool storage_pool_name -size disk_size -compressed -deduplicated
  4. To create a thin-provisioned volume that has deduplication enabled in a data reduction pool, enter the following command:
    mkvolume -name name -pool storage_pool_name -size disk_size -thin -deduplicated
  5. To map the volume to a host, enter the following command:
    mkvdiskhostmap -host host_name vdisk_name
    where host_name is the name of the host and vdisk_name is the name of the volume.