Arrays

An array, also referred to as a managed array, is a group of storage devices that provides capacity for a pool. An array generally consists of 8 drives that are managed as a Redundant Array of Independent Disks (RAID).

Array properties

You can view the properties of an array in the Arrays by Pool table or the Array Properties window.

ID

The unique identifier for an array that is assigned by the system.

State

The status of an array.

Note: If you see a state that requires action to return to a normal state, go to the Events page for information about array state change events.

Unassigned: The array is not assigned to a pool; all of the drives in the array are in a normal state.
Formatting: One or more drives in the array are being formatted.
Unavailable: The array is not assigned to a pool and one or more of the drives are not in the normal state. This state prevents you from selecting the array for operation.
Normal: The array is assigned to a pool and none of the other states apply. This state is the preferred state for arrays in most cases.
Reserved: No new capacity can be allocated from the array.
Depopulating to unassign: Data is being deleted and the array is no longer assigned to a pool. Capacity that was allocated to the array is being migrated to other arrays in the pool.
Depopulating to reassign: Data is being deleted and the array is being assigned to another pool. Capacity that was allocated to the array is being migrated to other arrays in the pool.
Depopulating: Data is being deleted from the array. Capacity that was allocated to the array is being migrated to other arrays in the pool.
Configured: The array is configured with a storage type or RAID level. Unassign the array to unconfigure it.
Configuring: The array is being configured with a storage type and RAID level.
Reconfiguring: The drives in the array are being reformatted and repartitioned, and the array is not yet assigned to a pool.
Depopulation error: The depopulation of the array failed. If the array is reserved when this error occurs, it remains in the reserved state. Contact IBM® Hardware Support.
Internal error: An internal system error occurred and the problem cannot be determined. Contact IBM Hardware Support.
Degraded: One or more drives in the array are in a rebuild state. The array is not in the read-only, failed, repairing, or inaccessible state. Contact IBM Hardware Support
Read-only: One or more drives failed, but the array is not in a failed, repairing, or inaccessible state. An insufficient number of spares are left to support rebuild operations. Contact IBM Hardware Support.
Note: Continued write operations without redundancy can result in data loss.
Failed: Two or more drives in the array failed and the array is not in the repairing or inaccessible state. An insufficient number of drives are left in the array to rebuild the data that was lost on the failed drives. Contact IBM Hardware Support.
Repairing: The array was previously in a failed state, but is being repaired and is not accessible.
Inaccessible: One or more drives in the array cannot be accessed for reading or writing. Contact IBM Hardware Support.
Unknown: The state of the array cannot be determined. Contact IBM Hardware Support.

Pool

The pool that contains the array.

Capacity

The amount of capacity that the array contributes to the associated pool.

Note: An array must have a defined storage type and RAID level to determine capacity. Unassigned arrays do not typically list the capacity.

Storage type

The type of storage architecture, either fixed block (FB) for open systems hosts or count key data (CKD) for IBM Z hosts, for which an array is provisioned.

Open systems hosts use FB architecture, where the data for volumes is mapped over fixed-size blocks or sectors.

IBM Z hosts use CKD. CKD is a data recording format that uses self-defining record formats in which each record on a volume is represented by up to three fields:

A count field, which identifies the record and specifies its format
An optional key field, which can be used to identify the data area contents
An optional data field, which typically contains the user data

Because data record lengths can vary, the data records all have an associated count field that indicates the size of the key, if used, and the size of the data. The count field has the identification of the physical location in cylinder-head-record format, the length of the key, and the length of the data.

Drive capacity

The raw capacity of the drives in the array, before they are formatted and configured. For example, a drive might have a raw capacity of 146 GB before it is formatted and configured with a RAID level within an array.

Drive class

The classification and speed in RPMs (if specified) of the drives in the array. Drive class examples include enterprise 10k, enterprise 15k, nearline 7.2k, and flash drives.

DA pair

The two device adapters in the I/O enclosures that work together to provide redundancy for I/O requests for one or more storage enclosures to improve overall throughput. A DS8000® storage system can have a maximum of four DA pairs to support up to eight storage enclosures.

Node

The processor node (0 or 1) that manages all I/O for the array.

RAID level

A collection of two or more drives that provides data protection by using the techniques of striping, mirroring, or parity to drives.

RAID 5: One parity drive protects the data, allowing the RAID to continue to process read and write requests if up to one concurrent disk failure occurs. Both data and parity are striped over all drives in the RAID. Supports flash drive, enterprise 15k, and enterprise 10k drive classes.
RAID 6: Two parity drives protect the data, allowing the RAID to continue to process read and write requests if up to two concurrent disk failures occur. Both data and parity are striped over all drives in the RAID. Supports enterprise 15k and enterprise 10k, and nearline 7.2k drive classes.
RAID 10: Data is mirrored on two drives within the RAID, allowing the RAID to continue to process read and write requests if up to one concurrent disk failure occurs. Both data and mirror are striped over all drives in the RAID. Supports 400 GB flash cards.

Configuration

The number of spare (reserve), data, and parity (data protection) drives within the array.

Encryption

Indicates if the array is encrypted or not encrypted.

Rank

The rank in use by the array. A rank is divided into a number of fixed-size extents.

Extent size

The size of extents in the rank. For an open-systems hosts, an extent is 1 GB. In an IBM Z environment, an extent is the size of an IBM 3390 Mod 1 disk drive.

Drives

The number of drives in the array.

Spares

The number of drives that are reserved as spares within an array. These spare drives can be used to rebuild any array within the same DA pair as the array.

Volumes

The number of volumes that are associated with the array.