Storage pool Commands

The storage pool command family provides the ability to create and manage SSD storage pools. Storage pools are collections of solid-state disks (SSDs) that can be shared between multiple Flash Pool aggregates and between two nodes of an HA pair.

The use of SSD storage pools is optional. Flash Pool aggregates can use whole SSDs, or they can use SSD capacity from storage pools. When multiple aggregates share the SSD capacity from an SSD storage pool, there is a reduction in parity overhead and you have the ability to share high SSD performance across multiple aggregates and across both nodes of an HA pair. A storage pool contains a minimum of 3 and a maximum of 29 SSDs.

When an SSD storage pool is created using the storage pool create command, the SSDs are divided into four equal-sized partitions. The capacity of the group of disks is expressed in terms of allocation units. Each allocation unit is 25% of the capacity. The storage pool initially contains unprovisioned allocation units which can be displayed using the storage pool show-available-capacity command.

In an HA configuration, each node takes ownership of two allocation units representing 50% of the total capacity. If desired, the ownership of the allocation units can be adjusted using the storage pool reassign command before the capacity is used in an aggregate.

Storage pools do not have an associated RAID type. The RAID type is determined when an allocation unit is added to an aggregate using the storage aggregate add-disks command. A storage pool contains four allocation units, and they might be used in up to four aggregates. You can add multiple allocation units to a Flash Pool aggregate to increase its cache capacity.

The space in an SSD storage pool can be expanded by adding SSDs to the storage pool using the storage pool add command. The size of each of the four allocation units will expand by 25% of the capacity of the disks being added. For example, if an SSD with a usable size of 745 GB is added to a storage pool that is part of four aggregates, each aggregate will grow its cache or usable capacity by 186.25 GB. If a different allocation is desired, create a new SSD storage pool using the storage pool create command.

All storage pool available capacity can be provisioned into aggregates. Available capacity within a storage pool is not used to protect against a disk failure. In the case of an SSD failure or predicted failure, Data ONTAP moves a suitable whole spare SSD from outside the storage pool into the storage pool and begins the recovery process(using either reconstruction or Rapid RAID Recovery, whichever is appropriate).