Moving volumes to a data reduction pool

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The system supports migrating existing volumes to a data reduction pool with volume mirroring. Hosts I/O operations to the volume are not disrupted during migration.In environments where the system is comprised of older models that support compressed volumes in standard pools, these volumes must be migrated to data reduction pools before the system is upgraded.

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. For more information, see planning data reduction pools and deduplication.

You can move volumes in standard pools to data reduction pools to simplify management of reclaimed capacity. The data reduction pool tracks the unmap operations of the hosts and reallocates capacity automatically. The system supports volume mirroring to create a copy of the volume in a new data reduction pool. This method creates a copy of the volume in a new data reduction pool and does not disrupt host operations.

Using the management GUI

To migrate the volume to a data reduction pool, complete these steps:

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.
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.
Create a copy of the volume in the standard pool by completing these steps:
1. In the management GUI, select Pools > Volumes by Pools.
2. Select the existing pool that contains the volumes you want to migrate to the data reduction pool. Right-click the volume and select Add Volume Copy.
3. On the Add Volume Copy page, select the data reduction pool to create a copy of the volume. Copy 1 is the original volume in the original pool, while copy 2 is created in the data reduction pool. Ensure that either thin-provisioning or compressed is selected for the capacity savings. For the option that you select, 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.
4. Click Add.
5. Ensure that the copies are synchronized before you proceed to the next steps. On the Volumes page, ensure that Yes is displayed for copy 2 in the Synchronized column.
  Note: The time synchronization takes to complete depends on the size of the volume and system performance. You can increase the synchronization rate by right-clicking the volume and selecting Modify Mirror Sync Rate.
To complete the migration, remove the original volume copy by completing these steps:
1. In the management GUI, select Volumes > Volumes.
2. Right-click the volume copy and select Delete.
3. Click Yes to confirm the deletion.

Using the command-line interface

To migrate volumes to a data reduction pool in the command-line interface, complete these steps:

To create a data reduction pool, enter the following command:
```
mkmdiskgrp -name pool_name -ext extent_size -mdisk mdisk_id_list -datareduction yes
```
Where pool_name is the name of the pool, extent_size is the extent size of the pool, and mdisk_id_list is a list of MDisk IDs in the data reduction pool.
To create copies of the volume in the data reduction pool, enter the following command:
Compressed volume copy
```
addvdiskcopy -mdiskgrp mdisk_group_name -compressed -rsize disk_size -autoexpand vdisk_name
```
Thin-provisioned volume copy
```
addvdiskcopy -mdiskgrp mdisk_group_name -rsize disk_size -autoexpand vdisk_name
```
Thin-provisioned, deduplicated volume copy
```
addvdiskcopy -mdiskgrp mdisk_group_name -rsize disk_size -autoexpand -deduplicated vdisk_name
```
Compressed, deduplicated volume copy
```
addvdiskcopy -mdiskgrp mdisk_group_name -compressed -rsize disk_size -autoexpand -deduplicated vdisk_name
```
Where mdisk_group_name specifies the name of the data reduction pool created in Step 1 in which the copies reside and disk_size is an integer value in megabytes (MB). The vdisk_name variable is the name of the volume that is being copied.
To ensure that the copies of the volume are synchronized, enter the following command:
```
lsvdisk vdisk_name
```
Where vdisk_name is the name of the volume that contains the copies. In the command output, verify that the sync value is set to yes for the new volume copy, which indicates that the new volume copy is synchronized it the original copy.
To complete the migration, remove the original copy of the volumes from the original pool by entering the following command:
```
rmvdiskcopy -copy copy_id vdisk_name
```
Where copy_id is the system-assigned identifier for the volume copy and vdisk_name is the name of the original volume.