– If performance is of concern, use a storage pool with MDisks that share the same characteristics. Otherwise, the mirrored pair can be on external virtualized storage with lesser-performing MDisks. 

GLYPH<SM590000> Data Reduction Pool (DRP) volumes 

– When configuring DRP-based volumes, ther e are special considerations required and procedures to be followed. See Chapter 3, “Data reduction and tools” on page 23. 

## 4.6.3 Easy Tier 

IBM Easy Tier is a function that automatically and non-disruptively moves frequently accessed data from various types of MDisks to flash drive MDisks, thus placing such data in a faster tier of storage. Easy Tier supports four tiers of storage. 

The IBM FlashSystem 9100 supports the following tiers: 

GLYPH<SM590000> Tier 0 flash: Specifies a tier0_flash  IBM Flash Core Modules or an external MDisk for the newly discovered or external volume. 

GLYPH<SM590000> Tier 1 flash: Specifies a tier1_flash  (or flash SSD drive) for the newly discovered or external volume. 

GLYPH<SM590000> Enterprise tier: Enterprise tier exists when the pool contains enterprise-class MDisks, which are disk drives that are optimized for performance. 

GLYPH<SM590000> Nearline tier: Nearline tier exists when the pool contains nearline-class MDisks, which are disk drives that are optimized for capacity. 

Note:  In the IBM FlashSystem 9100 these Enterprise or Nearline drives would be in external arrays. All managed arrays on the IBM FlashSystem 9100 system contain either NVMe class drives in the IBM FlashSystem 9100 control enclosures, or SSD class drives in the SAS expansion enclosures. 

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

If the IBM FlashSystem 9100 control enclosure is used in an Easy Tier pool and is enabled on the pool, the node canisters will send encrypted, incompressible data to the NVMe drives. IBM Spectrum Virtualize software detects if an MDisk is encrypted by the FlashSystem 9100. Therefore, if an IBM FlashSystem 9100 control enclosure will be part of an encrypted easy-tier pool, encryption must be enabled on the IBM FlashSystem 9100 before  it is enabled in the Easy Tier pool. 

IBM Spectrum Virtualize does not attempt to encrypt data in an array that is already encrypted. This enables the hardware compression of the IBM FlashSystem 9100 to be effective if using the FCM type NVMe drives. However, there are cases in which using IBM FlashSystem 9100 software compression is preferred, such as if there is highly compressible data, (for example 3:1 or higher). In these cases, both encryption and compression can be done by the IBM FlashSystem 9100 node canisters. 

For more information about Easy Tier, see the IBM Redbooks publication Implementing the IBM System Storage SAN Volume Controller with IBM Spectrum Virtualize V8.1 , SG24-7933. In addition, see the Easy Tier function section in the FlashSystem 9100 IBM Knowledge Center. 

Storage pools have an Easy Tier setting that controls how Easy Tier operates. The setting can be viewed through the management GUI but can only be changed by the CLI. 

