The ESCON adapter in the DS8000 is a dual ported host adapter for connection to older zSeries hosts that do not support FICON. The ports on the ESCON card use the MT-RJ type connector.

Control units and logical paths

ESCON architecture recognizes only 16 3990 logical control units (LCUs) even though the DS8000 is capable of emulating far more (these extra control units can be used by FICON). Half of the LCUs (even numbered) are in server 0, and the other half (odd-numbered) are in server 1. Because the ESCON host adapters can connect to both servers, each adapter can address all 16 LCUs.

An ESCON link consists of two fibers, one for each direction, connected at each end by an ESCON connector to an ESCON port. Each ESCON adapter card supports two ESCON ports or links, and each link supports 64 logical paths.

ESCON distances

For connections without repeaters, the ESCON distances are 2 km with 50 micron multimode fiber, and 3 km with 62.5 micron multimode fiber. The DS8000 supports all models of the IBM 9032 ESCON directors that can be used to extend the cabling distances.

Remote Mirror and Copy with ESCON

The initial implementation of the ESS 2105 Remote Mirror and Copy function (better known as PPRC or Peer-to-Peer Remote Copy) used ESCON adapters. This was known as PPRC Version 1. The ESCON adapters in the DS8000 do not support any form of Remote Mirror and Copy. If you wish to create a remote mirror between a DS8000 and an ESS 800 or another DS8000 or DS6000, you must use Fibre Channel adapters. You cannot have a remote mirror relationship between a DS8000 and an ESS E20 or F20 because the E20/F20 only support Remote Mirror and Copy over ESCON.

ESCON supported servers

ESCON is used for attaching the DS8000 to the IBM S/390 and zSeries servers. The most current list of supported servers is at this Web site:

http://www.storage.ibm.com/hardsoft/products/DS8000/supserver.htm

This site should be consulted regularly because it has the most up-to-date information on server attachment support.

2.5.1 FICON and Fibre Channel protocol host adapters

Fibre Channel is a technology standard that allows data to be transferred from one node to another at high speeds and great distances (up to 10 km and beyond). The DS8000 uses Fibre Channel protocol to transmit SCSI traffic inside Fibre Channel frames. It also uses Fibre Channel to transmit FICON traffic, which uses Fibre Channel frames to carry zSeries I/O.

Each DS8000 Fibre Channel card offers four 2 Gbps Fibre Channel ports. The cable connector required to attach to this card is an LC type. Each port independently auto-negotiates to either 2 Gbps or 1 Gbps link speed. Each of the 4 ports on one DS8000 adapter can also independently be either Fibre Channel protocol (FCP) or FICON, though the ports are initially defined as switched point to point FCP. Selected ports will be configured to FICON automatically based on the definition of a FICON host. Each port can be either FICON or Fibre Channel protocol (FCP). The personality of the port is changeable via the DS Storage Manager GUI. A port cannot be both FICON and FCP simultaneously, but it can be changed as required.

38DS8000 Series: Concepts and Architecture

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IBM DS8000 manual Ficon and Fibre Channel protocol host adapters, Control units and logical paths, Escon distances