External storage systems

An external storage system, or storage controller, is a device that coordinates and controls the operation of one or more disk drives. A storage system synchronizes the operation of the drives with the operation of the system as a whole.

The system can manage a combination of internal and external storage and represents all the detected storage as MDisks. The management GUI can be used to configure both internally and externally attached storage. Data that is stored on external storage can also be migrated to internal storage, simplifying data and storage management. The system supports Fibre Channel and iSCSI-attached storage systems. Fibre Channel attached storage is automatically detected through the SAN fabric, but iSCSI storage must be manually added to the system for virtualization. The system does not require a license for its own control and expansion enclosures. However, a license is required for each enclosure of any external storage systems that are being virtualized. For example, if the system is made up of one control enclosure, one expansion enclosure, and one virtualized storage system that is itself made up of two enclosures, two licenses are required.

Avoid splitting arrays into multiple logical disks at the storage system level. Where possible, create a single logical disk from the entire capacity of the array and map that to the system.

If you have configured logical unit names (LUNs) on your external storage systems, it is not possible for the system to determine this name, because the namespace is local to the external storage system. However you can use the external storage system WWNNs and LUN IDs to identify each device. This unique ID can be used to associate MDisks on the system to the corresponding LUNs on the external storage system.

Select Pools > External Storage in the management GUI to view all MDisks detected by the system. The MDisks are organized by the external storage system that presents them. To display the unique ID that is associated with the external storage system, use the filter function in the management GUI to display the UID column. If new external storage is added to the system, select Actions > Discover storage. If no MDisks display, ensure that you have cabled the system correctly to the external storage system.

Note: You can also issue the lsmdisk command to display information about the MDisks that are visible to the system. The command output contains detailed information about the node canister with the lowest node ID number. However, both node canisters have access to the MDisks.

The size of an MDisk cannot be changed after it is added to a pool. If the size of the LUN that is presented by the storage system is reduced to below the size of the MDisk, the MDisk is taken offline by the system. If the size of the LUN that is presented by the storage system is increased, the system does not use the additional space. To increase the storage capacity that is managed on a storage system, create a new LU on the storage system and add the MDisk that represents this LU to the pool. Additionally, if you delete a RAID that is being used by the system, the pool goes offline and the data in that group is lost.

In general, pools that consist of single-port attached systems are not supported. However, HP StorageWorks MA and EMA systems that contain array partitions can only be attached to the system through a single-port attach mode.