A clustered system, which was known as a cluster, is a group of up to eight IBM Storwize  V7000 canisters (two in each system) that presents a single configuration, management, and  service interface to the user. A cold extent is an extent of a volume that does not get any performance benefit if it is moved  from a hard disk drive (HDD) to a Flash disk. A cold extent also refers to an extent that needs  to be migrated onto an HDD if it is on a Flash disk drive. Compression is a function that removes repetitive characters, spaces, strings of characters,  or binary data from the data that is being processed and replaces characters with control  characters. Compression reduces the amount of storage space that is required for data. A compression accelerator is hardware onto which the work of compression is offloaded from  the microprocessor. While the cluster is operational, a single node in the cluster is appointed to provide  configuration and service functions over the network interface. This node is termed the  configuration node. This configuration node manages the data that describes the  clustered-system configuration and provides a focal point for configuration commands. If the  configuration node fails, another node in the cluster transparently assumes that role. A Consistency Group is a group of copy relationships between virtual volumes or data sets  that are maintained with the same time reference so that all copies are consistent in time. A  Consistency Group can be managed as a single entity. A container is a software object that holds or organizes other software objects or entities. For thin-provisioned volumes that are configured to automatically expand, the unused real  capacity that is maintained. For thin-provisioned volumes that are not configured to  automatically expand, the difference between the used capacity and the new real capacity. Copied is a FlashCopy state that indicates that a copy was triggered after the copy  relationship was created. The Copied state indicates that the copy process is complete and  the target disk has no further dependency on the source disk. The time of the last trigger  event is normally displayed with this status. A counterpart SAN is a non-redundant portion of a redundant SAN. A counterpart SAN  provides all of the connectivity of the redundant SAN, but without the 100% redundancy. IBM  Storwize V7000 canisters are typically connected to a “redundant SAN” that is made up of  two counterpart SANs. A counterpart SAN is often called a SAN fabric.  Counterpart SAN Copied state Contingency capacity Container Consistency Group Configuration node Compression accelerator Compression Cold extent Clustered system (Storwize V7000) Appendix C. Terminology  773