
S T 3 9 1 7 5 F C    SEAGATE
                                                      Native|  Translation
                                                      ------+-----+-----+-----
Form                 3.5"/HH               Cylinders        |     |     |
Capacity form/unform  9170/      MB        Heads            |     |     |
Seek time   / track      /     ms          Sector/track     |     |     |
Controller           FC-AL FIBRE CHANNEL   Precompensation
Cache/Buffer               KB              Landing Zone
Data transfer rate          MB/S int       Bytes/Sector      512
                            MB/S ext
Recording method                                    operating  | non-operating
                                                  -------------+--------------
Supply voltage                  Temperature *C                 |
Power: sleep              W     Humidity     %                 |
       standby            W     Altitude    km                 |
       idle               W     Shock        g                 |
       seek               W     Rotation   RPM
       read/write         W     Acoustic   dBA
       spin-up            W     ECC        Bit
                                MTBF         h
                                Warranty Month
Lift/Lock/Park     YES          Certificates                                  

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                      G   E   N   E   R   A   L
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SEAGATE   FC-AL INTERFACE


 An Overview of Fibre Channel
 ---------------------------

 Introduction
 ------------
 Everyone has accepted the fact that we have moved into the Age of
 Information. In this paradigm information itself is a commodity, and
 therefore there is great value in its efficient disbursement.

 Unfortunately, industry has placed greater value in creating
 information, than distributing it. We often hear about new machines
 which are capable of performing prodigious calculation at the blink
 of an eye. New reports of ever faster computers are commonplace.

 Sharing this information, however, has become a priority only
 recently. It seems that although we have moved into the Age of
 Information, one of our biggest challenges is to efficiently
 distribute the information for everyone to use.

 Luckily, a viable solution is at hand. Conceived and supported by
 such industry giants as IBM, Hewlett-Packard, and Sun Microsystems,
 the Fibre Channel is aimed at providing an inexpensive, flexible and
 very high-speed communications system. Most of the popular network
 implementations today can claim to have any two of these elements.
 Since Fibre Channel encompasses all three, it has everything
 necessary to become a resounding success.

 Not the Network
 Fibre Channel has significant advantages over common networks. The
 first difference is speed. The fastest network implementations today
 support transfer data at a little over 100 megabits per second. For
 smaller data files, where a single computer is directly communicating
 with a file server, such speeds are adequate. However, for realtime
 video and sound, or systems where two machines must operate on common
 data even 200 megabits per second is hopelessly inadequate. Fiber
 Channel provides significantly higher rates, from 10 to 250 times
 faster than a typical Local Area Network (LAN). In fact, Fibre
 Channel can transfer data at speeds exceeding 100 megabytes, or 800
 megabits, per second. This speed is sufficient to allow transfer of a
 1024x768 image with 24-bit color at 30 frame per second, and CD-
 quality digital sound.

 This overcomes the bandwidth limitation, which is probably the most
 serious impediment  for LAN performance. As the number of computers
 communicating on a common network increases, the amount of data
 packets increases accordingly.

 This is because data on a LAN is common to all computers on that
 network. The software must decide if a particular message is relevant
 for a particular machine. When several machines are communicating
 with one another, every other machine on the network must contend
 with all of the messages. As the number of messages increases, the
 load for the entire system is increased.

 Fiber channel is a switched system. Much like a telephone system, a
 connection is established between only the parties that need to
 communicate. These parties can share the entire bandwidth of Fibre
 Channel, since they do not have to contend with messages not relevant
 to their communication. LANs attempt to compensate for this by
 increasing the transfer speed, which places an even greater burden on
 the software. Since all protocol for Fibre Channel is handled by
 the hardware, the software overhead is minimal. Fibre Channel also
 supports full parallelism, so if greater capacity is needed, more
 lines can be added. The common analogy for showing the advantages of
 parallelism is the effect of doubling the number of lanes on a
 freeway instead of doubling the speed limit.

 The physical distance between computers is another limiting factor
 for conventional LANs. Ethernet cables usually have a limit of 1000
 feet between machines whereas Fibre Channel can support a link
 between two up to 10 kilometers apart.

 Finally, Fibre Channel is not software intensive. All of the
 essential functions are  handled by hardware, freeing the computer's
 processor to attend to the application at hand. Even the error
 correction for transmitted data is handled by the Fibre Channel
 hardware. In standard LANs this requires precious processor
 resources.


 Advantages for Computing
 ------------------------
 The obvious advantage for Fibre Channel is to facilitate
 communication between machines. Several workstations clustered
 together already surpass the speed and capacity of a VAX, and begin
 to rival the power of a super computer, at a much lower cost. The
 power of concurrent processing is awesome. For example, a single
 neuron inside our brain is much less complex, and operates far slower
 than a common 286 processor. However, millions of neurons working in
 parallel can process information much faster than any processor known
 today. Networking simple logical units, and operating them in
 parallel offers advantages simply unavailable for the fastest single
 processor architectures. These shared architectures require a huge
 amount of communication and data sharing which can only be handled by
 high-speed networks. Fibre Channel not only meets these requirements,
 but meets them inexpensively.

 The hardware industry is partly responsible for the I/O bottleneck.
 By using the processor speed as the primary focus for their sales
 efforts, the bus speeds have languished. With respect to the new
 class of processors, current system bus speeds  are greatly lagging.
 This is something like building a mill which can process 1000 pounds
 of grain a day, and supplying that mill with a single donkey. There
 is little use for a fast processor that spends most of its time
 waiting for data to act upon.  Whether this data comes from disc
 drives, peripherals, or even other processors, today's bus speeds
 would leave most processors idle, and the next generation of
 processors will be many times faster. Fiber Channel provides the
 data transfer capability which can keep current and upcoming
 processors busy.


 Impact on Mass Storage
 ----------------------
 Today's fastest interfaces are capable of transferring data at around
 20 megabytes per second. However, this speed rating is only for
 transferring data. All protocol intercommunication occurs at  much
 slower speeds, resulting in a lower effective data transfer rates,
 typically around 11 megabytes per second. This represents about
 one-tenth of Fibre Channel's current capability. Fibre Channel drives
 do not suffer from device protocols occurring at slower speeds, since
 all communication occurs at 100 megabytes per second, including
 device intercommunication. In addition to this, the drive itself can
 be placed up to 10 kilometers away from the computer. This would have
 two effects on the way mass storage is implemented.

 First, the amount of data a machine could receive would only be
 limited to the transfer speed of the drive. For high performance disc
 arrays this could exceed 50 megabytes per second. Machine and disc
 storage could finally work to provide real-time, full motion video
 and sound for several machines simultaneously. With Fibre Channel's
 ability to work across long distances, these machines could
 conceivably reside many miles apart. For medical applications,
 computer design centers, and real-time networks such as reservations
 systems, this capability would be invaluable.

 Second, such support for transmitting data over large distances would
 allow disc drives to be placed away from the computer itself. This
 would allow for centralized data resource areas within a business
 office, simplifying everything from site planning to maintenance
 procedures. Indeed a centralized data resource center would be
 possible for an entire office complex.

 The development of the Loop will also provide a huge advantage in
 implementing large capacity disc sub systems. The Fast/Wide SCSI
 specification has a theoretical upper limit of 16 total devices
 attached to a single host. The practical maximum is 6 devices. Fibre
 Channel supports a theoretical limit of 256 devices for a common
 host, with a practical implementation of 64 devices. This practical
 limit is a very conservative figure, and implementation with more
 devices are easily possible. The Loop allows system designers to
 build high capacity configurations, well into the terabyte range,
 with much lower overall cost.

 Finally, Fibre Channel is a serial communications device which has
 two immediate advantages. First, the cabling necessary to
 interconnect Fibre Channel devices is very inexpensive when compared
 to SCSI cabling. Fibre Channel cabling is also much easier to
 connect, and replace than SCSI cables, which simplifies the entire
 process of integration and maintenance for a high capacity data
 storage system. For corporations that are currently grappling with a
 the complexity of installation, and high-cost of SCSI cables, this
 feature will prove invaluable for cutting costs and simplifying
 installation and upkeep.

 Secondly, implementing Fibre Channel requires less space on the
 circuit board than SCSI drives. This reduced space requirement would
 allow the drive designers to include extended features which cannot
 currently be implemented. For example, a 3.5-inch form-factor drive
 with Fibre Channel could be designed with  dual-port capability, a
 feature necessary for use with many mainframes and mini-computers.
 The space saved on the circuit board by using Fibre Channel would
 allow for the extra connector and additional circuitry needed for
 dual-port drives.


 Conclusion
 ----------
 The Fibre Channel will provide the corporations with data in much the
 same way the freeway system provided motorists mobility. Access to a
 vast, interconnected information network which is fast, inexpensive,
 and flexible. With the adoption of Fibre Channel as an open ANSI
 standard, its effect on the horizon of computing will be nothing
 short of revolutionary.

 We have become very good at processing data; Fibre Channel allows us
 to move it. The ability to share information will provide the impetus
 for communication, design and development on a scale not previously
 possible. By facilitating the fabled data-highway, Fibre Channel
 will accelerate  to the Age of Information, as the steam engine moved
 us into the Age of Industry.


