Serial Storage Architecture (SSA) was a serial transport protocol used to attach disk drives to server computers . It was developed by IBM employee Ian Judd in 1990 to provide data redundancy for critical applications. SSA was deployed in server RAID environments, where it was capable of providing for up to 80 MB /s of data throughput, with sustained data rates as high as 60 MB/s in non-RAID mode and 35 MB/s in RAID mode.
7-476: SSA was promoted as an open standard by the SSA Industry Association, unlike its predecessor, the first generation Serial Disk Subsystem. A number of vendors including IBM, Pathlight Technology and Vicom Systems produced products based on SSA. It was also adopted as an American National Standards Institute (ANSI) X3T10.1 standard. SSA devices are logically SCSI devices and conform to all of
14-573: A reported $ 265 million. Said Rahmani became VP of R&D at ADIC after the acquisition. One of the significant products from Pathlight was the SAN Gateway, which provided multi-directional bridging between multiple Parallel SCSI ports and multiple Fibre Channel ports. IBM teamed with Pathlight to provide the SAN Data Gateway (IBM Product 2108-G07 ) and SAN Data Gateway Router (IBM Product 2108-R03 ). This article about
21-512: Is 20 megabytes per second in each direction per channel, with up to two channels per cable. The transport layer protocol is non-return-to-zero , with 8B/10B encoding (10 bits per character). Higher protocol layers were based on the SCSI -3 standard. Pathlight Technology Pathlight Technology was a pioneer in the field of Storage Area Networks . Based in Ithaca, NY , Pathlight
28-439: The SCSI command protocols. SSA was invented by Ian Judd of IBM in 1990. IBM produced a number of successful products based upon this standard before it was overtaken by the more widely adopted Fibre Channel protocol. All the components in a typical SSA subsystem are connected by bi-directional cabling. Data sent from the adaptor can travel in either direction around the loop to its destination. SSA detects interruptions in
35-597: The loop and automatically reconfigures the system to help maintain connection while a link is restored. Up to 192 hot swappable hard disk drives can be supported per system. Drives can be designated for use by an array in the event of hardware failure. Up to 32 separate RAID arrays can be supported per adaptor, and arrays can be mirrored across servers to provide cost-effective protection for critical applications. Arrays are connected by thin and inexpensive copper cables situated up to 25 metres apart, allowing subsystems to be located in secure, convenient locations, far from
42-479: The server itself. The copper cables used in SSA configurations are round bundles of two or four twisted pairs, up to 25 metres long and terminated with 9-pin micro-D connectors. Impedances are 75 ohm single-ended, and 150 ohm differential. For longer-distance connections, it is possible to use fiber-optic cables up to 10 km (6 mi) in length. Signals are differential TTL . The transmission capacity
49-667: Was formed in 1994 as a spin-out from Ironics, a manufacturer of VME computer, IO and memory boards. Pathlight was involved in the development of Serial Storage Architecture products, and in Fibre Channel products. Pathlight merged with ADIC in 2001. Pathlight Technologies was founded by Said Rahmani in 1994. Between 1997 and 2000, Rand Capital participated in four rounds of investments in Pathlight Technology. ADIC acquired Pathlight in January 2001 for
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