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 models of control enclosures.

The system supports the following tiers of drives:
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.

For control enclosures that support NVMe architecture, NVMe-attached drives are both self-encrypting and self-compressing. With self-encrypting drives that use NVMe architecture, data encryption is completed in the drive itself. Data encryption keys remain on the drive without being stored in system memory. In addition, the system supports automatic locks of encrypted drives when the system or drive is powered down. When the drive or system restarts, a master key is required to unlock the drive and continue I/O operations. The system also supports a cryptographic erase feature that enables a drive to be erased quickly if the drive is no longer active in an array, but might contain sensitive data. A cryptographic erase is started when a drive is formatted. If the NVMe-attached drive is a member of an encrypted array, formatting the drive completes a cryptographic erase of the drive.

Like self-encrypting drives that use NVMe architecture, self-compressing drives are compressed in the drive itself. The system also supports compression through data reduction pools. If your configuration uses both of these compression methods, ensure that volumes in data reduction pools are created with compression enabled. If compression is not enabled on volumes in data reduction pools, accurate usable capacity for the systems is difficult to determine. Both of the self-encrypting and self-compressing drives are only available on certain models of control enclosures that support NVMe-attached drives. Verify that your model supports NVMe-attached drives.

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.

When a drive is moved between drive slots, the drive ID is maintained unless its Use property is changed to Unused. In the command line interface, the use parameter, which is specified on the chdrive command, determines if the drive can be formed into an array.

To access information about drives in the management GUI, select Monitoring > System. On the System - Overview page, click the directional arrow next to the enclosure that contains the drives. On the Enclosure Details page, select Drive under Front View to highlight and display information on the drives. To display information about the drives in the command-line interface, use the lsdrive command.

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