Easy Tier

The system includes IBM® Easy Tier®, which is a function that responds to the presence of high performance drives in a storage pool that also contains hard disk drives (HDDs). The system automatically and nondisruptively moves frequently accessed data from slower to faster tiers of storage.

Easy Tier eliminates manual intervention when you assign highly active data on volumes to faster responding storage. In this dynamically tiered environment, data movement is seamless to the host application regardless of the storage tier in which the data belongs. However, you can manually change the default behavior. For example, you can turn off Easy Tier on pools that have any combination of the four types of MDisks.

Use the following guidelines when you group similar disks:

Group MDisks with equal performance in a single tier of a pool.
Group similar arrays in a single tier. For example, configure all 6 + P RAID-5 arrays in one tier of a pool.
Group MDisks from the same storage systems types in a single tier of a pool.
Group MDisks that use the same type of underlying physical disk in a single tier of a pool. For example, group MDisks by Fibre Channel or SATA.
When possible, include similar sized MDisks in a storage pool tier to make it easier to balance the MDisks in that storage pool tier.

The system supports these tiers:

Storage Class Memory: Storage Class Memory tier exists when the pool contains drives that use persistent memory technologies that improve endurance and speed of current flash storage device technologies.
Tier 0 flash: Tier 0 flash tier exists when the pool contains high performance flash drives.
Tier 1 flash: Tier 1 flash tier exists when the pool contains tier 1 flash drives. Tier 1 flash drives typically offer larger capacities, but slightly lower performance and write endurance characteristics.
Enterprise tier: Enterprise tier exists when the pool contains enterprise-class MDisks, which are disk drives that are optimized for performance.
Nearline tier: Nearline tier exists when the pool contains nearline-class MDisks, which are disk drives that are optimized for capacity.

All MDisks belong to one of the tiers, which includes MDisks that are not yet part of a pool.

A child pool inherits the Easy Tier settings from its parent pool. You cannot change the Easy Tier settings on a child pool. You can only change them on a parent pool.

If a pool contains one type of MDisk, Easy Tier goes into balancing mode. When the pool contains multiple types of MDisks, Easy Tier is automatically turned on. The local MDisks are classified as storage class memory, tier 0 flash, tier 1 flash, enterprise, or nearline drives. The system supports storage class memory, tier 0, and tier 1 flash drives. Storage class memory drives use Non-Volatile Memory Express (NVMe) technology that provides faster performance than the traditional SSDs but are slower than dynamic random-access memory (DRAM)-based drives. Tier 0 flash drives are higher-cost flash drives that provide high performance for read and write operations. Tier 1 flash drives are lower-cost flash drives that have large capacity but lower performance and write endurance characteristics.