ESCON Part 1
RAID Recovery - ESCON
Enterprise Systems Connection (ESCON) is a fiber optic channel created by IBM to connect mainframe computers to peripheral storage devices such as disks and tapes. Developed in 1990, ESCON was the successor of copper-based parallel Bus & Tag channel technology. Bus & Tag used a parallel environment, but ESCON uses serial bit-by-bit technology, in which the communication protocol is implemented through a series of special characters.
Being an optic fiber-based technology, ESCON considerably reduces installation and maintenance costs. They are more reliable too. Fiber cables are 100 times lighter than the Bus & Tag cables. They have reduced bulk and have fewer pin connections. Also they have reduced packet loss and distortion, and are free from signal skew.
ESCON is a vendor-proprietary technology; it was not based on any existing standards.
Topology
The topology of ESCON consists of a control unit and channel attachment. These are attached in a switched point-to-point arrangement. Because of this, it is possible to create multiple connections between channels and control units, without requiring permanent physical connections. The point-to-point nature of the connections also allows physical changes to the I/O configuration alongside normal operations.
ESCON technology is a half-duplex serial interface. It operates at a speed up to 17 million bits per second (Mbps) and achieves a maximum distance of 43 kilometers. Data rate on the link is up to 200 Mbps.
