In the simplest terms, iSCSI enables the transport of SCSI commands and data over an  Internet Protocol network, based on IP routers and Ethernet switches. iSCSI is a block-level  protocol that encapsulates SCSI commands into Transmission Control Protocol/Internet  Protocol (TCP/IP) packets and uses an IP network, rather than requiring expensive FC host  bus adapters (HBAs) and a SAN fabric infrastructure. The major functions of iSCSI include encapsulation and the reliable delivery of CDB  transactions between initiators and targets through the Internet Protocol network, especially  over a potentially unreliable IP network. Every iSCSI node in the network must have an iSCSI name and address. Consider the  following points: IBM Real-time Compression is an attractive solution to address increasing data storage  requirements for power, cooling, and floor space. When applied, IBM Real-time Compression  can significantly save storage space because more data is stored in rack space so fewer  storage enclosures are required to store a data set. IBM Real-time Compression provides the  following benefits: Chapter 2. System overview  35 GLYPH<SM590000> Disk space savings are immediate. The space reduction occurs when the host writes the  data. This process is unlike other compression solutions, in which some or all of the  reduction is realized only after a post-process compression batch job is run. – Reduced software licensing for more functions in the system. More data stored per  enclosure reduces the overall spending on licensing. – Reduced power and cooling r equirements. More data is stored in a system, which  requires less power and cooling per gigabyte or used capacity. GLYPH<SM590000> Overall savings in operational expenses. More data is stored in a rack space, so fewer  storage expansion enclosures are required to store a data set. This reduced rack space  has the following benefits: GLYPH<SM590000> No changes to the environment are required. IBM Real-time Compression is part of the  storage system. GLYPH<SM590000> Compression for replicated/mirrored data. Remote volume copies can be compressed in  addition to the volumes at the primary storage tier. This process also reduces storage  requirements in Metro Mirror and Global Mirror destination volumes.  GLYPH<SM590000> Compression for active primary data. IBM Real-time Compression can be used with active  primary data.  GLYPH<SM590000> An  iSCSI address  specifies not only the iSCSI name of an iSCSI node, but a location of  that node. The address consists of a host name or IP address, a TCP port number (for the  target), and the iSCSI name of the node. An iSCSI node can have any number of  addresses, which can change at any time, particularly if they are assigned by way of  Dynamic Host Configuration Protocol (DHCP). An IBM SAN Volume Controller node  represents an iSCSI node and provides statically allocated IP addresses. GLYPH<SM590000> An  iSCSI name  is a location-independent, permanent identifier for an iSCSI node. An  iSCSI node has one iSCSI name that stays constant for the life of the node. The terms  initiator name  and  target name  also refer to an iSCSI name. 2.5.20 Real-time Compression