Logical configuration with DS8000 Storage Management GUI

Before you configure your storage system with the DS8000 Storage Management GUI, it is important to understand the storage concepts and sequence of system configuration.

Figure 1 illustrates the concepts of configuration.

Figure 1. Logical configuration sequence
Logical configuration of fixed block (FB) storage for open systems hosts consists of creating pools and volumes. Logical configuration of count key data (CKD) storage for IBM Z hosts consists of creating pools, LSSs, and volumes.

The following concepts are used in storage configuration.

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).
A storage pool is a collection of storage that identifies a set of storage resources. These resources provide the capacity and management requirements for arrays and volumes that have the same storage type, either fixed block (FB) or count key data (CKD).
A volume is a fixed amount of storage on a storage device.
The logical subsystem (LSS) that enables one or more host I/O interfaces to access a set of devices.
A host is the computer system that interacts with the storage system. Hosts defined on the storage system are configured with a user-designated host type that enables the storage system to recognize and interact with the host. Only hosts that are mapped to volumes can access those volumes.

Logical configuration of the storage system begins with managed arrays. When you create storage pools, you assign the arrays to pools and then create volumes in the pools. FB volumes are connected through host ports to an open systems host. CKD volumes require that logical subsystems (LSSs) be created as well so that they can be accessed by an IBM® Z host.

Pools must be created in pairs to balance the storage workload. Each pool in the pool pair is controlled by a processor node (either Node 0 or Node 1). Balancing the workload helps to prevent one node from doing most of the work and results in more efficient I/O processing, which can improve overall system performance. Both pools in the pair must be formatted for the same storage type, either FB or CKD storage. You can create multiple pool pairs to isolate workloads.

When you create a pair of pools, you can choose to automatically assign all available arrays to the pools, or assign them manually afterward. If the arrays are assigned automatically, the system balances them across both pools so that the workload is distributed evenly across both nodes. Automatic assignment also ensures that spares and device adapter (DA) pairs are distributed equally between the pools.

If you are connecting to a IBM Z host, you must create a logical subsystem (LSS) before you can create CKD volumes.

You can create a set of volumes that share characteristics, such as capacity and storage type, in a pool pair. The system automatically balances the volumes between both pools. If the pools are managed by Easy Tier®, the capacity in the volumes is automatically distributed among the arrays. If the pools are not managed by Easy Tier, you can choose to use the rotate capacity allocation method, which stripes capacity across the arrays.

If the volumes are connecting to a IBM Z host, the next steps of the configuration process are completed on the host.

If the volumes are connecting to an open systems host, map the volumes to the host, add host ports to the host, and then map the ports to the I/O ports on the storage system.

FB volumes can only accept I/O from the host ports of hosts that are mapped to the volumes. Host ports are zoned to communicate only with certain I/O ports on the storage system. Zoning is configured either within the storage system by using I/O port masking, or on the switch. Zoning ensures that the workload is spread properly over I/O ports and that certain workloads are isolated from one another, so that they do not interfere with each other.

The workload enters the storage system through I/O ports, which are on the host adapters. The workload is then fed into the processor nodes, where it can be cached for faster read/write access. If the workload is not cached, it is stored on the arrays in the storage enclosures.