Drives

The system supports various different types of drives and drive classes. These drives are used to create arrays that provide capacity for pools and volumes.

A drive object represents the physical drive. The system creates this object automatically and assigns a drive ID when a supported drive is detected through the serial-attached SCSI (SAS) or Non-Volatile Memory express (NVMe) protocols. Some hardware models use SAS-attached drives for storage while others use NVMe-attached drives for storage, but these drives are not interchangeable and cannot be created in the same array. NVMe is a drive interface technology that offers increased bandwidth and parallelism over SAS, useful for high demand storage. NVMe-attached drives are only supported by certain node models as virtualized external storage and are presented as storage class memory tiers. These types of drives on external storage require a license per storage capacity unit (SCU) for the tier. Only SAN Volume Controller 2145-SV2 and 2145-SA2 nodes support these drives as storage class memory (SCM) tiers on external storage systems that support the NVMe technology.

The system supports the following tiers of drives:
Storage Class Memory
Storage Class Memory drives use persistent memory technologies that improve endurance and reduce latency of current flash storage device technologies. All SCM drives use NVMe architecture.
Tier 0 flash
Tier 0 flash drives are high-performance flash drives that process read and write operations and provide faster access to data than Enterprise or nearline drives. For most Tier 0 flash drives, the system monitors their wear level and issues warnings when the drive is nearing replacement. Some NVMe-attached drives, such as IBM FlashCore® Module drives, are considered Tier 0 flash drives.
Tier 1 flash
Tier 1 flash drives are lower-cost flash drives, typically with larger capacities, but slightly lower performance and write endurance characteristics. The system monitors their wear level and issues warnings when the drive is nearing replacement.
Enterprise disks
Enterprise disks are disk drives that are optimized for performance.
Nearline disks
Nearline disks are disk drives that are optimized for capacity.

The management GUI creates arrays based on these different types of tiers and the features the drive supports. Drives with similar characteristics are created to form arrays and the management GUI ensures arrays are configured correctly to ensure performance and endurance.

Note: Do not replace a drive unless the drive fault LED is on or you are instructed to do so by a fix procedure.