Easy Tier Heat Map Transfer Utility

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A heat map is a workload activity metric that is calculated for each extent in a logical volume. The workload activity is expressed as a temperature gradient from hot (high activity) to cold (low activity). Use of the heat map transfer utility requires the Easy Tier® monitoring function to be enabled at each of the primary and secondary storage systems that are involved in the heat map transfer.

The heat map transfer utility periodically transfers Easy Tier heat map information from primary to secondary storage systems. The secondary storage system generates migration plans based on the heat map data and current physical configuration of the secondary storage system. In this way, the performance characteristics of the secondary storage are consistently updated to reflect that of primary storage. Multiple secondary storage systems are supported. Alternatively, you can have multiple primary storage systems that are associated with a single secondary storage system. It is recommended that the secondary storage system has the same physical configuration as the primary storage system. Secondary storage systems are then workload optimized based on primary storage system usage, with no performance penalties if data recovery is necessary.

Note: Currently, the heat map transfer utility does not support replicating tier assignment instructions of the Easy Tier Application from the primary to secondary storage systems. To reflect the same tier assignment on the secondary storage systems, issue the same tier assignment commands on the secondary storage systems.

Data that occurs in the I/O cache layer (including the storage and server-side cache) is not monitored by Easy Tier and not reflected in an Easy Tier heat map.

If a workload failover occurs, the secondary storage system:

Uses the heat map data that is transferred from the primary storage system.
Maintains performance levels equivalent to the primary storage system while the primary storage system is unavailable.

Note: Without the same physical configuration, a secondary storage site is able to replicate the heat map data, but is unlikely to be able to replicate the performance characteristics of the primary storage system.

The heat map transfer utility runs either on a separate Windows or Linux® host, or on IBM® Copy Services Manager. From the host, the heat map transfer utility accesses the primary and secondary storage sites by using an out-of-band IP connection. Transfer of heat map data occurs through the heat map transfer utility host.

The heat map transfer utility imports the heat map data from the primary storage system, and analyzes this data to:

Identify those volumes that have a peer-to-peer remote client (PPRC) relationship.
Determine the type of PPRC relationship that exists. The relationship can be Metro Mirror, Global Copy, Global Mirror, or Metro Global Mirror.

In a Metro Global Mirror environment, DS8000® storage systems can be added under the heat map transfer utility management. Under this management, the heat map transfer utility treats the systems as Metro Mirror plus Global Mirror (Global Copy and FlashCopy) relationships. The utility detects the Metro Mirror and Global Mirror relationships automatically and performs the heat map data transfer for the relationships on the systems separately.

There are restrictions in a heat map transfer in Metro Global Mirror environment. For example, assume volumes A, B, C, and D, where:

Volume A is the Metro Mirror primary (or source) volume
Volume B is the Metro Mirror secondary (or target) volume and Global Mirror primary volume at the same time.
Volume C is the Global Mirror secondary volume and FlashCopy source volume at the same time. The FlashCopy target volume is referred to as the D volume.
- Heat map data is transferred only from volumes A and B and volumes B and C. No heat map data is transferred to the volume D copy or any additional test copies that you create.
- Heat map data that is transferred to volume C might lag for a maximum of 36 hours from volume A. After the transfer to volumes A and B is complete, it might take a maximum of 24 hours (the default Easy Tier heat map data generation interval) for volume B to generate heat map data. There is a 12-hour interval (the default heat map transfer interval) for the volumes B and C data transfer.

The heat map information for the selected volumes is then periodically copied from the primary storage system to the heat map transfer utility host (default copy period is 12 hours). The heat-map-transfer utility determines the target secondary storage system that is based on PPRC volume mapping. The utility transfers the heat-map data to the associated secondary storage systems. The heat-map data is then imported to the secondary storage system, and Easy Tier migration plans are generated based on the imported and existing heat map. Finally, the result of the heat map transfer is recorded (in memory and to a file).

To enable heat map transfer, the heat-map transfer-control switch that is on the secondary storage system needs to be enabled

-ethmtmode
enabled

. This is the default mode. Use the DSCLI command chsi to enable or disable heat map transfer:

chsi -ethmtmode enable | disable

The scope of heat map transfer is determined by the Easy Tier automatic mode setting:

To automatically transfer the heat map data and manage data placement for logical volumes in multi-tiered pools, use the Easy Tier control default settings (-etmonitor automode, -etautomode tiered).
To automatically transfer the heat map data and manage data placement for logical volumes in all pools, use the Easy Tier control settings (-etmonitor all, -etautomode all).

Note: For PPRC relationships by using Global Mirror, Easy Tier manages data placement of the Global Copy target and FlashCopy® source only, and does not manage data placement for a FlashCopy target that is involved in the Global Mirror relationship.

If you want to run an Easy Tier evaluation on both the primary and secondary storage systems, set the Easy Tier control on both storage systems to "monitor only" (-etmonitor all). The heat map transfer utility then automatically transfers the heat map data and uses this data to generate an Easy Tier report, without changing the data layout on either of the storage systems.