Before you configure your DS6000™ series, it is important to understand IBM® terminology for storage concepts and the storage hierarchy.
In the storage hierarchy, you begin with a disk. Logical groupings of four disks form an array site. Logical groupings of one or two array sites form an array. After you define your array storage type as CKD or fixed block, you can create a rank. A rank is divided into a number of fixed-size extents. If you work with an open-systems host, an extent is 1 GB. If you work with IBM eServer™ zSeries® or S/390® systems, an extent is the size of an IBM 3390 Mod 1 disk drive.
After you create ranks, your physical storage can be considered virtualized. Virtualization dissociates your physical storage configuration from your logical configuration, so that volume sizes are no longer constrained by the physical size of your arrays.
The available space on each rank is divided into extents. The extents are the building blocks of the logical volumes. An extent is striped across all disks of an array.
Extents of the same storage type are grouped together to form an extent pool. Multiple extent pools can create storage classes that provide greater flexibility in storage allocation through a combination of RAID types, DDM size, DDM speed, and DDM technology. This allows a differentiation of logical volumes by assigning them to the appropriate extent pool for the desired characteristics. Different extent sizes for the same device type (for example, count-key-data or fixed block) can be supported on the same storage unit, but these different extent types must be in different extent pools.
A logical volume is composed of one or more extents. A volume group specifies a set of logical volumes. By identifying different volume groups for different uses or functions (for example, SCSI target, FICON control unit, remote mirror and copy secondary volumes, FlashCopy® targets, and Copy Services), access to the set of logical volumes that are identified by the volume group can be controlled. Volume groups map hosts to volumes. Figure 1 shows a graphic representation of the logical configuration sequence.
When volumes are created, you must initialize logical tracks from the host before the host is allowed read and write access to the logical tracks on the volumes. An internal volume initialization process allows quicker access to logical volumes that are used as host volumes and source volumes in Copy Services relationships, such as FlashCopy or Remote Mirror and Copy relationships. Volumes are not available as target volumes for Copy Services relationships until the volumes have been fully initialized. After volume initialization is complete and successful, you can use the target volumes to establish Copy Services relationships. Initialization requests can fail if the initialization is performed on volumes that are participating in existing Copy Services relationships.
The storage management software can be used in real-time or simulated modes. When you are connected to storage devices over your network, you can use the Real-time Manager to manage your hardware or configure your storage. When you want to work offline, you can use the Simulated Manager to create or import a configuration. This lets you export a configuration that you have already created to a system when it reaches your site.
The custom configuration option is ideal if you want to customize your configuration. The Express Configuration option shortens and simplifies the configuration process, but only allows you to create one host. This is ideal if you want only one host and you want to quickly and easily set up and configure your storage because most storage-appropriation decisions have already been made.