S T 1 5 1 5 0 F C B A R R A . - 4 F C SEAGATE
Native| Translation
------+-----+-----+-----
Form 3.5"/HH Cylinders 3711| | |
Capacity form/unform 4294/ 5062 MB Heads 21| | |
Seek time / track 8.5/ 0.8 ms Sector/track | | |
Controller FIBRE CHANNEL DUAL Precompensation
Cache/Buffer 1024 KB MULTI-SEGMEN Landing Zone
Data transfer rate 6.000 MB/S int Bytes/Sector 512
100.000 MB/S ext
Recording method RLL 1/7 operating | non-operating
-------------+--------------
Supply voltage 5/12 V Temperature *C 5 50 | -40 70
Power: sleep W Humidity % |
standby W Altitude km |
idle 18.4 W Shock g |
seek W Rotation RPM 7200
read/write W Acoustic dBA
spin-up W ECC Bit
MTBF h 800000
Warranty Month 60
Lift/Lock/Park YES Certificates CSA,EN60950,FCC,IEC950,UL1...
**********************************************************************
L A Y O U T
**********************************************************************
SEAGATE ST15150FC INSTALLATION GUIDE 83329070, REV. A 9/95
+---------------------------------------------+
| |
| |
| |
| INTERFACE |
| +-----------------------+ |
+----------+XXXXXXXXXXXXXXXXXXXXXXX+----------+
+-----------------------+
40-PIN
**********************************************************************
J U M P E R S
**********************************************************************
SEAGATE ST15150FC INSTALLATION GUIDE 83329070 REV. A 9/95
Jumper Setting
==============
REAR VIEW
40 pin I/O and DC Power Wall/bracket Connection
| Female
+-----|----------+ TOP (HDA)
----------+ ++++++++++++++ +-----------
+-1------------20+ BOTTOM
Notes on 40 pin I/O connector:
+12V = pins 2, 3, 4, 21
+5V = pins 19, 20, 40
GND = pins 6, 22, 23, 26, 29, 32, 35
Mating FC connector: AMP US p/n: 787317-1 straight-in, Male 40-pin
FRONT VIEW
----------
Reserved. Shipped with cover installed. Do not remove. Do not install
jumpers! |
| ++---- RESERVED
| ||+--- Fault LED
| |||+-- Port B Bypass LED
| ||||+- Port A Bypass LED
TOP (HDA) ++---+-++++1+
---PCB----------------------+::::|::::::+--------
++ BOTTOM +-J6-++++---+
++ |||+++
| ||| +-- Ground
LED + ||+---- Active LED
|+----- Ground
+------ Remote LED (pin-11 +5v)
ST15150FC drives have two ports for connection to two independent
loops. Both loops may be active, but only one of these ports may be
receiving or originating data at any one time. Do not connect both
ports to the same loop.
Connecting remote LEDs
----------------------
NOTE
THE LYJX-0 BOARD DOES NOT HAVE THE J20 CONNECTOR!!
You can connect remote LEDS using J20.
Connect the anode (usually the longer LED connector) to the +5V pin,
and the cathode to the appropriate LED output pin. For example, if
you want to attach an LED which lights up when the drive is active
(reading or writing), connect the LEDs anode connector to J20 pin 6
and the cathode to J20 pin 3.
+-------------------+------------------------------------------+
| | |
| +---+ |
| +---+ |
| | |
| +-----+J20 | |
| |* * 1| | |
| |* * 2| | |
| +-----+ | |
+-------------------+------------------------------------------+
+-----+J20
|o o *| Port A Bypass LED
|o o o|
+-----+
+-----+J20
|o o o| Port B Bypass LED
|o o *|
+-----+
+-----+J20
|o * o| Active LED
|o o o|
+-----+
+-----+J20
|o o o| Fault LED
|o * o|
+-----+
+-----+J20
|* o o| GROUND
|o o o|
+-----+
+-----+J20
|o o o| +5 VOLT
|* o o|
+-----+
**********************************************************************
I N S T A L L
**********************************************************************
SEAGATE ST15150FC INSTALLATION GUIDE 83329070 REV. A 9/95
Notes On Installation
=====================
Drive orientation
-----------------
The drive may be mounted in any orientation. All drive performance
characterizations, however, have been done with the drive in
horizontal (discs level) and vertical (drive on its side) orienta-
tions, which are the two preferred mounting orientations.
Installation direction
----------------------
horizontally vertically
+-----------------+ +--+ +--+
| | | +-----+ +-----+ |
| | | | | | | |
+-+-----------------+-+ | | | | | |
+---------------------+ | | | | | |
| | | | | |
| | | | | |
+---------------------+ | +-----+ +-----+ |
+-+-----------------+-+ +--+ +--+
| |
| |
+-----------------+
The drive will operate in all axis (6 directions).
Installation
------------
ST15150FC disc drive installation is a plug-and-play process. There
are no jumpers, switches, or terminators on the drive which need to
be set. Simply plug the drive into the host's 40-pin Fibre Channel
backpanel connector (FC-SCA)-no cables are required.
The FC-AL interface is used to select drive ID and all option
configurations for devices on the loop.
If multiple devices are on the same FC-AL and physical addresses
are used, set the device selection IDs (SEL IDs) on the backpanel
so that no two devices have the same selection ID. This is called
the hard assigned arbitrated loop physical address (AL_PA). There
are 125 AL_PAs available. If you set the AL-PA on the backpanel to
any value other than 0, the device plugged into the backpanel's
SCA connector inherits this AL_PA. In the event you don't success-
fully assign unique hard addresses (and therefore have duplicate
selection IDs assigned to two or more devices), the FC-AL generates
a message indicating this condition. If you set the AL-PA on the
backpanel to a value of 0, the system issues a unique soft-
assigned physical address automatically.
Loop initialization is the process used to verify or obtain an
address. The loop initialization process is performed when power
is applied to the drive, when a device is added or removed from the
FC loop, or when a device times out attempting to win arbitration.
- Set all option selections in the connector prior to applying
power to the drive. If you change options after applying power
to the drive, recycle the drive power to activate the new settings.
- It is not necessary to low level format this drive. The drive is
shipped from the factory low level formatted in 512-byte sectors.
You need to reformat the drive only if you want to select a
different sector size or if you select a different spare sector
allocation scheme.
Do not touch the connector pins or any components on the control
board without observing static-discharge precautions. Always handle
the drive by the frame only.
Mount the drive to the host system's chassis using four 6-32UNC
screws. Two mounting holes are in each side of the drive and there
are four holes in the bottom of the drive.
Cooling
-------
Cabinet cooling must be designed by the customer so that the ambient
temperature immediately surrounding the drive will not exceed
temperature conditions.
Air flow
--------
The rack, cabinet, or drawer environment for the Barracuda 4FC drive
must provide cooling of the electronics and head and disc assembly
(HDA). You should confirm that adequate cooling is provided using
the temperature measurement guidelines described below.
The drive should be oriented, or air flow directed, so that the
least amount of air flow resistance is created while providing air
flow to the electronics and HDA. Also, the shortest possible path
between the air inlet and exit should be chosen to minimize the
travel length of air heated by the drive and other heat sources
within the rack, cabinet, or drawer environment.
The air flow patterns are created by one or more fans, either
forcing or drawing air as shown in the illustrations. Other air
flow patterns are acceptable as long as the temperature
measurement guidelines are met.
To confirm that the required cooling for the electronics and HDA
is provided, place the drive in its final mechanical configuration,
perform random write/read operations and, after the temperatures
stabilize, measure the case temperature of the components listed
below.
Drive mounting
--------------
Mount the drive using the bottom or side mounting holes. If you
mount the drive using the bottom holes, ensure that you do not
physically distort the drive by attempting to mount it on a stiff,
non-flat surface.
The allowable mounting surface stiffness is 80 lb/in (14.0 N/mm).
The following equation and paragraph define the allowable mounting
surface stiffness:
80 lb in k = = or F x 14.0 N mm
where k is the mounting surface stiffness (units in pounds or
newton) and x is the out-of-plane distortion (units in inches
or millimeters). The out-of-plane distortion (x) is determined
by defining a plane with three of the four mounting points fixed
and evaluating the out-of-plane defection of the fourth mounting
point when a known force (F) is applied to the fourth point.
Grounding
---------
Signal ground (PCB) and HDA ground are connected together in the
Barracuda 4 family drives, do not separate this connection.
Maximizing the conductive contact area between HDA ground and
system ground may reduce radiated emissions. A bracket shield
with tapped holes is available to system integrators. This shield
makes it easier to attach a braid or similar high-frequency
grounding device. If you do not want the system chassis to be
connected to the HDA/PCB ground, you must provide a nonconductive
(electrically isolating) method of mounting the drive in the host
equipment; however, this may increase radiated emissions and is the
system designer's responsibility.
Termination
-----------
The reference index signal (SSREF+) is terminated with a 2.21K ohm
resistor. Each drive has a termination resistor located on the Main
PCB. The terminator resistor is not removable and is always in the
circuit. Back-feeding of current is prevented by a diode.
Cache operation
---------------
Of the 1,024 Kbytes physical buffer space in the drive, 998 Kbytes
can be used as a cache. The cache can be divided into logical
segments from which data is read and to which data is written.
The drive keeps track of the logical block addresses of the data
stored in each segment of the cache. If the cache is enabled (see
RCD bit in the Fibre Channel Arbitrated Loop Product Manual), data
requested by the host with a read command is retrieved from the
cache, if possible, before any disc access is initiated. Data
in contiguous logical blocks immediately beyond that requested
by the Read command can be retrieved and stored in the cache
for immediate transfer to the initiator on subsequent read
commands. This is referred to as the prefetch operation. Since
data that is prefetched may replace data already in the cache
segment, an initiator can limit the amount of prefetch data to
optimize system performance. The drive never prefetches more
sectors than the number specified in bytes 8 and 9 of Mode page 08h
(see Fibre Channel Arbitrated Loop Product Manual). If the cache is
not enabled, 998 Kbytes of the buffer are used as a circular buffer
for read/ writes, with no prefetch operation and no segmented cache
operation.
The following is a simplified description of the prefetch/cache
operation:
Case A_read command is received and the first logical block is
already in cache:
1. Drive transfers to the initiator the first logical block
requested plus all subsequent contiguous logical blocks that
are already in the cache. This data may be in multiple segments.
2. When a requested logical block is reached that is not in any
segment, the drive fetches it and any remaining requested
logical block addresses from the disc and puts them in a segment
of the cache. The drive transfers the remaining requested logical
blocks from the cache to the initiator in accordance with the
"buffer-full" ratio specification given in Mode Select Disconnect/
Reconnect parameters, page 02h (see the Fibre Channel Arbitrated
Loop Product Manual).
3. The drive prefetches additional logical blocks contiguous to
those transferred in step 2 above and stores them in the segment.
The drive stops filling the segment when the maximum prefetch
value has been transferred (see the Fibre Channel Arbitrated
Loop Product Manual).
Synchronized spindle operation
------------------------------
Synchronized spindle operation allows several drives operating from
the same host to operate their spindles at the same synchronized
rotational rate. Drives operating in a system in synchronized mode
increase the system capacity and transfer rate in a cost-effective
manner.
Each drive in the system can be configured by the host (using a
Mode Select command) to operate in either the master or slave mode.
Drives can be reconfigured by the host any time after power-up to
be master or slave by use of the Mode Select command Rigid Disc
Drive Geometry page. The master provides the reference signal to
which all other drives phaselock, including the master. There is
only one master per system, and that can be a drive or the host
computer. All drives may be configured as slaves allowing the host
to provide the reference signal.
Each drive can be configured for the nonsynchronized mode in
which it ignores any reference signal that might be present_this
is the default mode as shipped from the factory. The connection of
the synchronized reference signal to the host is required only if
the host is to provide the reference signal. If the host does not
provide the reference signal, the host should not be connected.
Hot plugging the drive
----------------------
Inserting and removing the drive on the FC-AL will disrupt loop
operation. The disruption occurs when the receiver of the next
device in the loop must synchronize to a different input signal.
FC error detection mecha-nisms, character sync, running disparity,
word sync, and CRC are able to detect any error. Recovery is
initiated based on the type of error.
The Barracuda 4FC disc drive defaults to the FC-AL Monitoring
state, Pass-through state, when it is powered-on by switching the
power or hot plugged. The control line to an optional port bypass
circuit (external to the drive), defaults to the Enable Bypass
state. If the bypass circuit is present, the next device in the
loop will continue to receive the output of the previous device to
the newly inserted device. If the bypass circuit is not present,
loop operation is temporarily disrupted until the next device starts
receiving the output from the newly inserted device and regains
synchronization to the new input.
The Pass-through state is disabled while the disc performs self
test of the FC interface. The control line for an external port
bypass circuit remains in the Enable Bypass state while self test
is running. If the bypass circuit is present, loop operation may
continue. If the bypass circuit is not present, loop operation
will be halted while the self test of the FC interface runs.
When the self test completes successfully, the control line to the
bypass circuit is disabled and the drive enters the FC-AL Monitoring
state, Pass-though state. The receiver on the next device in the loop
must synchronize to output of the newly inserted drive.
If the self test fails, the control line to the bypass circuit
remains in the Enable Bypass state.
Note: It is the responsibility of the systems integrator to assure
that no temperature, energy, or voltage hazard is presented during
the hot connect/disconnect (hot plug) operation. Discharge the
static electricity from the drive carrier prior to inserting it
into the system.
Temperature
-----------
a. Operating
The MTBF specification for the drive (800,000 hours) is based on
operating at a local ambient temperature of 95*F (35*C).
Occasional excursions to drive ambient temperatures to 122*F
(50*C) may occur without impact to specified MTBF. The enclosure
for the drive should be designed such that the case temperatures
at the locations specified in Figures 11 and 12 are not exceeded.
Air flow is needed to achieve these temperature values. Continual
or sustained operation at case temperatures above these values
may degrade MTBF.
The drive meets all specifications over a 41*F to 122*F (5*C to 50*C)
drive ambient temperature range with a maximum gradient of 36*F
(20*C) per hour when the case temperature limits specified above are
not exceeded.
b. Non-operating
Non-operating temperature should remain between -40*F to 158*F
(-40*C to 70*C) package ambient with a maximum gradient of 36*F
(20*C) per hour. This assumes that the drive is packaged in the
shipping container designed by Seagate.
**********************************************************************
F E A T U R E S
**********************************************************************
SEAGATE ST15150FC INSTALLATION GUIDE 83329070 REV. A 9/95
Barracuda 4FC drives support the Fibre Channel Arbitrated Loop
and SCSI Fibre Channel Protocol specifications to the extent
described in this manual. The Fibre Channel Arbitrated Loop
Product Manual (part number 77767496) describes the general Fibre
Channel Arbitrated Loop characteristics of this and other Seagate
Fibre Channel drives.
Standards
---------
The Barracuda 4FC disc drive is designed to be a UL recognized
component per UL1950, CSA certified to CSA C22.2 No 950-M89, and
VDE certified to VDE 0805 and EN60950.
The Barracuda 4FC disc drive is supplied as a component part. It
is the responsibility of the subsystem designer to meet EMC/
regulatory requirements established by the FCC, DOC, and VDE.
Engineering test characterizations of radiated emissions are
available from the Seagate safety department.
General description
-------------------
Barracuda 4FC drives are random access storage devices designed to
support the Fibre Channel Arbitrated Loop (FC-AL) and SCSI Fibre
Channel Protocol as described in the ANSI specifications, this
document, and the Fibre Channel Arbitrated Loop Product Manual
(part number 77767496) which describes the general interface
characteristics of this drive.
You can view the Fibre Channel interface simply as a transport
vehicle for the supported command set (ST15150FC drives use the
SCSI command set). In fact, the Fibre Channel interface is unaware
of the content or meaning of the information being transported. It
simply packs the SCSI commands in packets, transports them to the
appropriate devices, and provides error checking to ensure that the
information reaches its destination accurately.
The head and disc assembly (HDA) is environmentally sealed at the
factory. Air recirculates within the HDA through a non-replaceable
filter to maintain a contamination-free HDA environment.
Never disassemble the HDA. This exploded view is for information
only. Do not attempt to service items in the sealed enclosure
(heads, media, actuator, etc.) as this requires special facilities.
The drive contains no parts replaceable by the user and opening the
HDA for any reason voids your warranty.
Barracuda 4FC drives use a dedicated landing zone at the innermost
radius of the media to eliminate the possibility of destroying or
degrading data by landing in the data zone. The heads automatically
go to the landing zone when power is removed from the drive.
An automatic shipping lock prevents potential damage to the heads and
discs that results from movement during shipping and handling. The
shipping lock disengages and the head load process begins when power
is applied to the drive.
Barracuda 4FC drives decode track 0 location data from the dedicated
servo surface to eliminate mechanical transducer adjustments and
related reliability concerns.
The drives also use a high-performance actuator assembly design that
provides excellent performance with minimum power dissipation.
Standard features
-----------------
Barracuda 4FC drives have the following standard features:
- Integrated dual port FC-AL controller
- Support for FC-AL (Fibre Channel Arbitrated Loop)
- Differential copper FC drivers and receivers
- Downloadable firmware using the FC-AL interface
- Drive selection ID and configuration options are set on the FC-AL
backpanel, T-card, or through interface commands. Jumpers are not
required on the drive.
- FC world-wide name uniquely identifies the drive and each port
- Supports up to 16 initiators
- User-selectable logical block size (180 to 4,096 bytes)
- Reallocation of defects on command (Post Format)
- User-selectable number of spare sectors per cylinder
- Industry standard 3.5-inch full-high form factor dimensions
- Programmable sector reallocation scheme
- Flawed sector reallocation at format time
- Programmable autowrite and read reallocation
- Reallocation of defects on command (post format)
- 96-bit Reed-Solomon error correction code
- Sealed head and disc assembly (HDA)
- No preventive maintenance or adjustments required
- Dedicated head landing zone
- Automatic shipping lock
- Automatic thermal compensation
- Embedded Grey Code track address to eliminate seek errors
- Self-diagnostics performed at power on
- 1:1 interleave
- Zone bit recording (ZBR)
- Vertical, horizontal, or top down mounting
- Dynamic spindle brake
- 998 Kbyte data buffer
Media description
-----------------
The media used on the drive has a diameter of approximately 95 mm
(approximately 3.7 inches). The aluminum substrate is coated with
a thin film magnetic material, overcoated with a proprietary
protective layer for improved durability and environmental
protection.
Performance
-----------
- Programmable multi-segmentable cache buffer
- 106.3 Mbytes/sec maximum instantaneous data transfers
- 7,200 RPM spindle; average latency = 4.17 msec
- Command queuing of up to 64 commands
- Background processing of queue
- Supports start and stop commands
- Provides synchronized spindle capability
- Adaptive seek velocity; improved seek performance
Reliability
-----------
- 800,000 hour MTBF (Class A computer room environment)
- Fibre Channel (FC) interface transports SCSI protocol through CRC
protected frames
- LSI circuitry
- Balanced low mass rotary voice coil actuator
Unformatted and formatted capacities
------------------------------------
The standard OEM models are formatted to 512 bytes per block.
ST15150FC drives have nine (9) spare sectors per cylinder and one
spare cylinder per unit.
Users having the necessary equipment may modify the data block
size before issuing a format command and obtain different
formatted capacities than those listed. User-available capacity
also depends on the spare reallocation scheme you select. See the
Mode Select command and the Format command in the Fibre Channel
Arbitrated Loop Product Manual (part number 77767496).
Factory-installed accessories
-----------------------------
OEM standard drives are shipped with the Barracuda 4FC Installation
Guide (part number 83329070).
Factory-installed options
-------------------------
You may order the following items which are incorporated at the
manufacturing facility during production or packaged before
shipping:
- Black plastic front panel with green lens (part number 70553702).*
- Black plastic front panel with red lens (part number 70553701).*
- Single-unit shipping pack. The drive is normally shipped in bulk
packaging to provide maximum protection against transit damage.
Units shipped individually require additional protection as
provided by the single unit shipping pack. Users planning
single unit distribution should specify this option.
* You may order other front panel colors. Each panel has a single
rectangular LED indicator lens that, when glowing, indicates
the drive is selected.
User-installed accessories
--------------------------
The following accessories are available. All kits may be installed
in the field.
- Front panel kit (green lens), part number 70869751.
- Single-unit shipping pack kit.
- Adapter accessory frame kit, part number 75790701. (adapts a
3.5-inch drive to fit in a 5.25-inch drive mounting space).
This kit contains the frame to allow a 3.5-inch drive to be
mounted in a 5.25-inch drive bay. It includes mounting hardware,
front panel with a green lens, an LED with cable that connects
to the remote LED connector, and installation instructions.
- Evaluation kit, part number 70935895. This kit provides an
adapter card ("T-card") to allow cable connections for two FC
interfaces and DC power. Two twin axial cables, 6-feet in length,
are included for the input and output connections to the FC
interfaces. A small DC fan is included for cooling.
All performance characteristics assume that thermal calibration is
not in process when the SCSI command is received. A SCSI command
being executed is not interrupted for thermal calibration. If
thermal calibration is in process when a SCSI command is received,
the command is queued until the compensation for the specific head
being calibrated completes. When compensation completes for the
specific head being calibrated, the first queued SCSI command is
executed.
Thermal calibration
-------------------
ST15150FC drives use an automatic thermal calibration (TCAL) process
to maintain accurate head alignment with the data cylinders. The host
system may choose to allow the drive to perform TCAL at the drive's
predefined intervals or the Rezero Unit command may be issued by the
host to reset the TCAL timer so that the host knows when the TCAL
will occur.
1. At power up and following a SCSI reset, the drive calibrates all
of the heads before any read or write com-mands are processed.
All heads are also calibrated during the SCSI Rezero Unit
command.
2. The drive delays 300 seconds before initiating any TCALs. No
TCALs occur during this delay period.
3. A single-head TCAL is then scheduled at 7.1 second intervals.
4. After the drive TCALs all of the heads, the interval is increased
to schedule a single head TCAL every 14.3 seconds.
5. The drive attempts to find an idle period of 25 to 50 milliseconds
prior to performing a single head TCAL. If this TCAL is delayed
for another interval of time, the drive forces the TCAL at the
next command boundary. This guarantees that no head will remain
uncalibrated for more than 600 seconds (2 * 21 heads * 14.3
seconds per head) and that no TCALs are closer together than the
interval time.
Note. Any TCAL performed during the "standard" retry sequence is
limited to the failing head and is disabled if the host has
selects a retry count of zero.
Defect and error management
---------------------------
The drive, as delivered, complies with this product manual. The read
error rates and specified storage capaci-ties are not dependent upon
use of defect management routines by the host (initiator).
Defect and error management in the SCSI protocol involves the drive
internal defect/error management and FC-AL system error considera-
tions (errors in communications between the initiator and the
drive). Tools for use in designing a defect/error management plan
are briefly outlined in this section. References to other sections
are provided when necessary.
Drive internal defects/errors
-----------------------------
Identified defects are recorded on the drive defects list tracks
(referred to as the primary or ETF defect list). These known defects
are reallocated during the initial drive format operation at the
factory. See the Format Unit command in the Fibre Channel
Arbitrated Loop Product Manual (part number 77767496). Data
correction by ECC is applied to recover data from additional
flaws if they occur.
Details of the SCSI commands supported by the drive are described in
the Fibre Channel Arbitrated Loop Product Manual. Also, more
information on the drive Error Recovery philosophy is presented in
the Fibre Channel Arbitrated Loop Product Manual.
Physical description
--------------------
ST15150FC drives may be connected in a loop together or with other
compatible FC-AL devices. A maximum of 127 devices may have
addresses; however, one of the addresses is reserved for a fabric
port switch device. This means 126 addresses are available for FC-AL
devices. More FC-AL compatible devices may physically reside on the
loop, but they will not be functional because they would not be able
to obtain valid addresses.
Port bypass circuits (PBCs) allow devices to be inserted into
unpopulated locations or removed from the loop with loop opera-
tion recovery after a brief disruption. These PBCs are located
external to the FC-AL device.
Power
-----
Power is supplied through the FC-SCA with support for +5 volts and
+12 volts. All of the voltage pins in the drive connector are the
same length.
Four 12 volt pins provide +12 volt power to the drive.
The current return for the +12 volt power supply is through the
common ground pins. The supply current and return current must be
distributed as evenly as possible among the pins. The maximum
current typically occurs while the drive motor is starting.
Three 5 volt pins provide logic power to the drive. The current
return for the +5 volt power supply is through the common ground
pins. The supply and return current must be distributed as evenly as
possible among the voltage and ground pins.
The mating connector pins use shorter contacts to achieve power
surge reductions and to aid in "hot plugging" the drives. There
are longer voltage contacts in the connector to enable the drive
filter capacitors to charge. Current to the drive through the long
charge pins is limited by the system in which the drive operates.
Three of the +12 volt pins are shorter to allow capacitive pre-
charging through the longer +12 volt charge pin. Two of the +5
volt pins are shorter to allow capacitive precharging through
the longer +5 volt charge pin.
Fault LED out
-------------
The Fault LED Out signal is driven by the drive when:
- the drive detects failure of both ports
- the drive detects an internal disc failure
- the drive receives the appropriate fault LED command from the
host
The Fault LED Out signal is designed to pull down the cathode of
an LED. The anode is attached to the proper +5 voltage supply
through an appropriate current limiting resistor. The LED and
the current limiting resistor are external to the drive.
Synchronized spindles interface
-------------------------------
The synchronized spindles interface (SSI) allows several drives
operating from the same host to operate their spindles at a
synchronized rotational rate.
Electrical description of the SSI
---------------------------------
The electrical interface consists of one digital TTL reference
index signal and ground. The reference index signal (SSREF+) is
an output if the drive is configured as a master and is an input
otherwise.
**********************************************************************
G E N E R A L
**********************************************************************
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.