Object overview
Before you set up your system, you must understand the concepts and the objects in the environment.
Volumes are logical disks that are presented by the systems. Each volume is associated with a particular I/O group. The nodes in the I/O group provide access to the volumes in the I/O group. When an application server performs I/O to a volume, it can access the volume with either of the nodes in the I/O group. Because each I/O group has only two nodes, the distributed cache is only two way.
Each MDisk is divided into a number of extents, which are numbered from 0, sequentially from the start to the end of the MDisk.
MDisks are collected into groups, which are known as storage pools.
Each volume is made up of one or two volume copies. Each volume copy is an independent physical copy of the data that is stored on the volume. A volume with two copies is known as a mirrored volume. Volume copies are made out of MDisk extents. All the MDisks that contribute to a particular volume copy must belong to the same storage pool.
A volume can be thin-provisioned. This means that the virtual capacity of the volume, as seen by host systems, can be different from the amount of storage that is allocated to the volume from MDisks, called the real capacity. Thin-provisioned volumes can be configured to automatically expand their real capacity by allocating new extents.
The system uses world wide port names (WWPNs) to identify the iSCSI and Fibre Channel ports on the host server. The system uses the iSCSI qualified name (IQN) to identify iSCSI hosts.