Planning for data reduction pools and deduplicated volumes

A deduplicated volume or volume copy can be created in a data reduction pool. When you implement deduplication, you must consider specific requirements in the storage environment.

Deduplication can be configured with volumes that use different capacity saving methods, such as thin-provisioning. Deduplicated volumes must be created in data reduction pools for added capacity savings. Deduplication is a type of data reduction that eliminates duplicate copies of data. Deduplication of user data occurs within a data reduction pool and only between volumes or volume copies that are marked as deduplicated. 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 create deduplicated volumes in an I/O group when no compressed volumes or volume copies are in regular storage pools (that is, when real-time compression is in use on that I/O group). Data reduction pool compressed volumes can coexist with real-time compressed volumes in the same I/O group.

You can migrate any type of volume from a standard pool to a data reduction pool. You can also migrate any existing real-time compressed volume to a data reduction pool. You can use volume mirroring to migrate data from a volume in a regular storage pool to a deduplicated volume in a data reduction pool. You can use the Add Volume Copy page in the management GUI or use the addvdiskcopy command to create a deduplicated, volume copy of an existing volume in a standard pool in a data reduction pool.

The following software and hardware requirements are needed for deduplication. There are also update and performance considerations.

Nodes must have at least 32 GB memory to support deduplication.
Nodes that have more than 64 GB memory can use a bigger deduplication fingerprint database, which might lead to better deduplication.
Avoid using Global Mirror with Change Volumes to or from a deduplicated volume
You can use the Data Reduction Estimation Tool (DRET) to estimate how much capacity you might save if a standard volume that a host can access was a deduplicated volume. 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.

Note: The Data Reduction Estimation Tool also provides some analysis of potential compression savings for volumes; however, it is recommended that you also use the management GUI or the command-line interface to run the integrated Comprestimator Utility to gather data for potential compression savings for volumes in data reduction pools.
To ensure that your intended use of deduplicated volumes can perform adequately for your application, refer to the Best Practice for Performance RedBook.

Real-time compression and deduplication are not supported in the same I/O group. However, data reduction pool compression and deduplication are supported on certain platforms.

Table 1 details the features that are supported on each platform.

Table 1. Supported compression features
Product	Platform	Node/canister memory (GBs)	Supported features
Product	Platform	Node/canister memory (GBs)	Real-time compression	Data Reduction Pools	Compression	Deduplication
SAN Volume Controller	2145-SV1 / 2147-SV1	64/128/192/256	Yes¹	Yes	Yes¹	Yes
	IBM Spectrum Virtualize	Any	Yes (dual CPU only)	Yes	Yes²	Yes (greater than 32 GB required)
	2145-DH8	32/64	Yes¹	Yes	Yes¹	Yes

Note: Real-time compression and data reduction compression is assumed to be supported within the same I/O group at the same time, unless the platform does not support compression or the matrix indicates otherwise.

1 - Requires compression hardware for new system.
2 - Compression in data reduction pools is supported by single or dual CPU. Dual CPU real-time compression restriction still applies. Does not support compression in data reduction pools and real-time compression in the same I/O group at the same time.