DWZZH 16-Bit UltraSCSI Hub
User’s Guide
EK–DWZZH–UG. D01
Compaq Computer Corporation
Achtung!
Dieses ist ein Gerät der Funkstörgrenzwertklasse A. In Wohnbereichen können bei Betrieb dieses
Gerätes Rundfunkstörungen auftreten, in welchen Fällen der Benutzer für entsprechende
Gegenmaßnahmen verantwortlich ist.
Attention!
Ceci est un produit de Classe A. Dans un environnement domestique, ce produit risque
de créer des interférences radioélectriques, il appartiendra alors à l’utilisateur de
prendre les mesures spécifiques appropriées.
JAPAN
USA
This equipment generates, uses, and may emit radio frequency energy. The equipment has been
type tested and found to comply with the limits for a Class A digital device pursuant to Part 15
of FCC rules, which are designed to provide reasonable protection against such radio frequency
interference. Operation of this equipment in a residential area may cause interference in which
case the user at his own expense will be required to take whatever measures may be required to
correct the interference. Any modifications to this device - unless expressly approved by the
manufacturer - can void the user’s authority to operate this equipment under part 15 of the FCC
rules.
Contents
Revision Record………………………………………………………………..vii
About This Guide………………………………………………………….…...ix
1
Introducing the DWZZH UltraSCSI Hub
1.1 UltraSCSI Hub Functions ......................................................................................1–1
1.2 Product Descriptions...............................................................................................1–2
1.2.1
1.2.2
1.2.3
DWZZH 3.5" SBB Hubs...................................................................................1–2
DWZZH 5.25" SBB Hubs.................................................................................1–4
SCSI Bus Components......................................................................................1–4
1.3 Product Specifications ............................................................................................1–5
2
Using the DWZZH UltraSCSI Hub
2.1 Large Hub Fair Arbitration .....................................................................................2–1
2.2 Large Hub Addressing Configurations ....................................................................2–2
2.3 Narrow Addressing Setting.....................................................................................2–3
2.4 Front Panel ............................................................................................................. 2–6
2.4.1
2.4.2
Fair Arb Disable ...............................................................................................2–6
Indicators..........................................................................................................2–7
2.5 Determining the Configuration...............................................................................2–7
2.6 Selecting the SCSI Cables.......................................................................................2–7
2.7 Placement of UltlraSCSI Hubs................................................................................2–7
3
SWCC and UltraSCSI Hubs...................................................................3–1
Glossary
Figures
1–1 DWZZH–21 or DWZZH-03 3.5" SBB Hub.............................................................1–2
1–2 DWZZH–21 Front Panel.........................................................................................1–3
1–3 DWZZH–03 Front Panel.........................................................................................1–3
1–4 DWZZH–05 5.25" SBB Hub..................................................................................1–4
2–1 DWZZH–05 SCSI ID Assignments.........................................................................2–3
2–2 DWZZH–05 SCSI Narrow ID Assignments ............................................................2–4
2–3 DWZZH–05 SCSI Narrow Addressing Jumper .......................................................2–5
2–4 DWZZH–05 SCSI Front Panel................................................................................2–6
EK–DWZZH–UG. D01
v
DWZZH 16-Bit UltraSCSI Hub
Figures (Cont’d)
3–1 Running One SWCC Agent for a Particular Storage Subsystem .............................3–3
Tables
1–1 DWZZH Hub Functional Specifications..................................................................1–5
2–1 Combinations of UltraSCSI Hubs and Devices in StorageWorks Shelves...............2–8
vi
EK–DWZZH–UG. D01
Revision Record
The Revision Record provides a concise publication history of this guide. It lists the guide
revision levels and release dates, and summarizes the changes.
The following revision history lists all revisions of this publication and their
effective dates. The publication part number is included in the Revision Level
column, with the last entry denoting the latest revision. This publication supports
the DWZZH 16-Bit UltraSCSI Hub.
Revision Level
Date
Summary of Changes
Original Release.
EK–DWZZH–UG. A01
EK–DWZZH–UG. B01
October 1997
April 1998
Change title page;
Add Section 1.2.2 describing
DWZZH–05 Hub;
Change Chapter 2 title from
“Installing” to “Using” and add
procedures for configuring a SCSI
bus using a DWZZH hub.
EK–DWZZH–UG. C01
July 1998
Change “SCSI” to “UltraSCSI”
throughout;
Add documents to list of Related
Documents;
Modify Figure 1-3;
Add installation recommendation
in introduction to Chapter 2;
Add Section 2.6, Placement of
UltraSCSI Hubs.
Add Chapter 3, SWCC and
UltraSCSI Hubs;
Add Glossary entries.
EK–DWZZH–UG. D01
vii
DWZZH 16-Bit UltraSCSI Hub
EK–DWZZH–UG. D01
October 1998
Change Section 2.1, add CAUTION
after Section 2.1.
Make minor changes to Section 2.3.3;
renumber Section 2.3.3 as Section 2.3.
Renumber Sections 2.3, 2.4, 2.5, and
2.6 as 2.4, 2.5, 2.6, and 2.7,
respectively.
viii
EK–DWZZH–UG. D01
About This Guide
This chapter tells you what this User’s Guide does, identifies the audience, describes the
structure and contents (chapter-by-chapter) briefly, and tells you how to get support and
services from Compaq.
This User’s Guide describes the purpose, function, operation, and use of the DWZZH
UltraSCSI Hub (the DWZZH Hub or the Hub). The DWZZH Hub allows the
connection of up to five ports on one logical SCSI bus.
Visit our Web Site for the Latest Information
Check our web site for the latest drivers, technical tips, and documentation. We
can be found in the technical area of our web page:
Audience
This guide is intended for end users and for Compaq employees responsible for
configuring, installing, and maintaining the StorageWorks subsystem and its
components.
Related Documentation
You should be familiar with the information contained in the following
documentation:
Document Title
Order Number
EK–BA350–CG
EK–BA350–UG
EK–SBBIO–UG
EK–ULTRA–CG
StorageWorks Solutions Configuration Guide
StorageWorks Solutions Shelf and SBB User’s Guide
StorageWorks SBB Shelf I/O Modules
StorageWorks UltraSCSI Configuration Guidelines
StorageWorks Solutions BA356–SB 16-bit Shelf User’s Guide EK–BA356–UG
Shared Storage Solutions Using UltraSCSI Hubs
EK–SMA21–AN
EK–SMA17–AN
Shared Storage for Windows NT Using UltraSCSI Hubs
Shared Storage for DIGITAL OpenVMS Using UltraSCSI Hubs EK–SMA19–AN
Shared Storage for DIGITAL UNIX Using UltraSCSI Hubs
EK–SMA20–AN
EK–DWZZH–UG. D01
ix
DWZZH 16–Bit UltraSCSI Hub
Document Structure
This guide contains the following chapters:
Chapter 1. Introducing the DWZZH UltraSCSI Hub
This chapter gives brief functional and physical descriptions of the DWZZH Hub
and lists significant product specifications.
Chapter 2. Using the DWZZH UltraSCSI Hub
This chapter gives the procedures for configuring a StorageWorks SCSI bus
using a DWZZH Hub.
Chapter 3. SWCC and UltraSCSI Hubs
This chapter provides important information concerning the use of StorageWorks
Command Console (SWCC) on SCSI buses that have an UltraSCSI hub. While
the information provided here is important, it is essential that you have read the
SWCC manual and release notes.
Glossary
The Glossary defines terms that are used frequently with StorageWorks and SCSI
bus components.
Support and Services
Who to contact in the Americas
Information and Product Questions:
Local Sales Office / StorageWorks Hotline
1-800-786-7967
Installation Support:
Contact the Compaq Distributor where the
Storage Solution was Purchased / Local
Compaq Sales Office.
Compaq Multivendor Customer Service (MCS)
Installation
Contact the Compaq Customer Support
Center (CSC).
Warranty
Contact the Compaq Customer Support
Center (CSC) for warranty service after
solution is installed and operating.
Remedial
Contact the Compaq Customer Support
Center (CSC)
Note: A Service Contract is recommended
when the equipment is out of warranty.
Contact the local Compaq Sales Office.
Customer Support Center (CSC)
1 800-354-9000
x
EK–DWZZH–UG. D01
About This Guide
Who to contact in Europe
Information and Product Questions,
Installation Support, and Installation:
Contact the Compaq Distributor or reseller
from whom the Storage Solution was
purchased.
For Warranty Service
For Remedial Service
See the Warranty Card packaged with the
product.
Contact the Compaq Distributor or reseller
from whom the Storage Solution was
purchased.
Note: A Service Contract is recommended
when the equipment is out of warranty.
Who to contact in Asia Pacific
For all services, contact the Compaq Distributor or reseller from whom the
equipment was purchased.
EK–DWZZH–UG. D01
xi
1
Introducing the DWZZH UltraSCSI Hub
This chapter describes the DWZZH Hub functions and available versions, and list the
Hub functional specifications.
The series of DWZZH Hubs are SCSI–2 and draft SCSI–3
(ANSI X379.2/91–10R3) compliant 16-bit converters capable of data transfer
rates of up to 40 Mbytes per second. The series of Hubs consists of the following:
•
DWZZH–21 and DWZZH–03 are 3.5" SBB (small) Hubs; the DWZZH–21
contains two single-ended and one differential UltraSCSI ports, while the
DWZZH–03 contains three differential UltraSCSI ports.
•
DWZZH–05 is a 5.25" SBB (large) Hub that contains 5 differential
UltraSCSI ports.
1.1 UltraSCSI Hub Functions
Most device SCSI buses are either 8-bit or 16-bit single-ended, physical buses.
Some controllers and hosts use differential buses and others use a single-ended
bus. Single-ended and differential physical buses are not compatible. The SCSI
protocol disables both buses when they are connected together. However, by
using an UltraSCSI Hub you can accomplish the following:
•
Connect a differential physical bus to a single-ended physical bus
(DWZZH–21 UltraSCSI Hub only).
•
•
Extend the maximum length of a SCSI bus.
Provide radial disconnect where remaining connections can continue to
operate.
•
Provide “fair” SCSI arbitration for host nodes (DWZZH-05 UltraSCSI HUB
only).
EK–DWZZH–UG. D01
1–1
DWZZH 16-Bit UltraSCSI Hub
1.2 Product Descriptions
There are two classes of DWZZH Hubs: 3.5" SBB Hubs, and 5.25" SBB Hubs.
1.2.1 DWZZH 3.5" SBB Hubs
The DWZZH small UltraSCSI Hub (Figure 1-1) comes in two versions.
•
DWZZH-21 contains two single–ended UltraSCSI connectors and one
differential UltraSCSI connector; Figure 1-2 illustrates the front panel.
•
DWZZH-03 contains three differential UltraSCSI connectors; Figure 1-3
illustrates the front panel.
CAUTION
Connecting a differential bus cable to the single-
ended connector, or a single-ended bus cable to
the differential connector causes the SCSI bus to
fail.
Figure 1–1 DWZZH–21 or DWZZH–03 3.5" SBB Hub
1–2
EK–DWZZH–UG. D01
Chapter 1. Introducing the DWZZH UltraSCSI Hub
Figure 1–2 DWZZH–21 Front Panel
NOTE
The single–ended symbol with the downward–
pointing diamond in Figure 1-2 indicates that the
lower two connectors are single–ended UltraSCSI
connections, while the differential symbol with the
right–pointing diamond indicates that the top
connector is a differential UltraSCSI connector.
Figure 1–3 DWZZH–03 Front Panel
NOTE
The differential symbol in Figure 1-3 indicates that
the three connectors are differential UltraSCSI
connectors.
EK–DWZZH–UG. D01
1–3
DWZZH 16-Bit UltraSCSI Hub
1.2.2 DWZZH 5.25" SBB Hubs
The DWZZH large UltraSCSI Hub (Figure 1-4) comes in a single version that
contains five differential UltraSCSI bus connectors.
CAUTION
any
Connecting a single-ended bus cable to
differential connector causes the SCSI bus to fail.
Figure 1–4 DWZZH–05 5.25" SBB Hub
1.2.3 SCSI Bus Components
To install a DWZZH UltraSCSI Hub you will need BN37A and BN38C series
SCSI cables. Refer to the
StorageWorks UltraSCSI Configuration Guidelines,
EK–ULTRA–CG for a complete list of the available cables.
,
1–4
EK–DWZZH–UG. D01
Chapter 1. Introducing the DWZZH UltraSCSI Hub
1.3 Product Specifications
Table 1-1 lists the functional specifications for the DWZZH Hub.
Table 1–1 DWZZH Hub Functional Specifications
Feature
Specification
SCSI ID
SCSI Addresses
The small UltraSCSI HUB does not use a SCSI ID.
The large UltraSCSI HUB uses SCSI ID 7 for
arbitration.
Overload Protection
DTERMPOWER
STERMPOWER
TERMPOWER is not supplied to the external ports
of the UltraSCSI HUB. Internal TERMPOWER is
protected via a resetable fuse. TERMPOWER must
be supplied from the remote connection to enable
each HUB port.
Shielding
Enclosure &
Connectors
Power-Up Reset
Shielded for ESD, EMI, and safety requirements
Automatically clears
•
•
•
Initiator detection circuit
Target detection circuit
BSY glitch filter
SCSI Bus Reset
Automatically clears
•
•
•
Initiator detection circuit
Target detection circuit
BSY glitch filter
Single-Ended SCSI Bus
Length
20 meters (66 feet) per segment
Ultra (20 megatransfers per
second or 40 MB/s)
Differential SCSI Bus Length
Data Timing
25 meters (82 feet) per segment
The relationship between the data and the control
signals is brought to SCSI compatibility before
transmission to the other SCSI bus.
High reliability SMT
Design
EK–DWZZH–UG. D01
1–5
DWZZH 16-Bit UltraSCSI Hub
Table 1–1 DWZZH Hub Functional Specifications (Cont’d)
Feature
Specification
Cable Fault
Glitch Elimination
DIFFSENSE support and port disable on cable fault
100% glitch free operation during power-up
BUSY GLITCH trap eliminates cable length constraint
due to wired-OR glitches on the BSY line
Termination
Singled-ended
Differential
Service
Active termination for 16bit operation.
Termination for 16bit operation.
There are no user servicable functions on these products.
Contact Digital service personnel all service.
Agency Approvals
UL, CSA, FCC Class B, TUV
Environmental Specifications
Relative Humidity
Operating Temperature
Storage Temperature (non-
operating)
10% to 85% non-condensing
10°C to 40°C (50°F to 104°F)
–40°C to 66°C (–40°F to 151°F)
Power Requirements
DWZZH
+5V
Input Current:
DWZZH-03
2.3 Amp
DWZZH-05
4.3 Amp
DWZZH-21
1.8 Amp
TERMPOWER
SCSI Connectors and Cables
Single-Ended
Differential
Cables
Supplied to internal terminators only.
Board mounted 68pin VHDCI SCSI connector
Board mounted 68pin VHDCI SCSI connector
BN37A and BN38C series shielded SCSI cables
1–6
EK–DWZZH–UG. D01
2
Using the DWZZH UltraSCSI Hub
This chapter discusses fair arbitration of the SCSI bus by the 5.25" SBB Hub, describes
addressing configurations, tells you how to use the large Hub front panel, and gives
guidelines for selecting the SCSI cables.
UltraSCSI Configuration guidelines are documented in EK-ULTRA-CG. These
guidelines include a list of all UltraSCSI components and the last few example
configurations include an UltraSCSI Hub. Refer to the configuration guidelines
for bus length and SCSI bus data transmission rates.
The UltraSCSI Hubs are designed to be installed in a StorageWorks Solutions
BA356 Shelf or in a StorageWorks BA370 shelf. The small UltraSCSI Hub can
be installed in any open SBB slot. The large UltraSCSI Hub can be installed in
any slots that will accommodate a 5.25" SBB. When installing UltraSCSI Hubs
in a BA370 shelf, it is recommended that UltraSCSI Hubs be installed in the
lower right hand device slots of the shelf, to allow better clearance for hot-
swapping of disk drives installed in the BA370 shelf. The small UltraSCSI Hub
does not consume a SCSI ID and uses the shelf only to provide its power and
mechanical support. The large UltraSCSI Hub uses SCSI ID 7 to control the fair
arbitration of the host port IDs and uses the shelf only to provide its power and
mechanical support.
2.1 Large Hub Fair Arbitration
The large Hub configurations utilize a modified SCSI arbitration algorithm. The
normal SCSI arbitration scheme is based on the SCSI ID. The highest priority
SCSI ID will always win arbitration This could have the effect of ‘starving’
lower priority SCSI ID requests on the bus.
SCSI ID 7 is RESERVED and may not be assigned to any SCSI device
connected to the UltraSCSI Hub, whether FairARB is enabled or disabled.
In order to allow up to four ‘host’ SCSI IDs to participate on a single SCSI bus, a
fair arbitration (fair arb) scheme is employed. Fair arb works by assigning SCSI
ID 7, the highest priority ID, to the Hub. When a SCSI arbitration phase occurs,
all the arbitrating IDs are captured in a register. The winning ID for this group
will be the highest priority ID. After this ID has been serviced, the ID will be
EK–DWZZH–UG. D01
2–1
DWZZH 16–Bit UltraSCSI Hub
removed from the group and at the next arbitration phase, the remaining highest
ID will be serviced. This will continue until all of the IDs in the group have been
serviced once. All requests from IDs not contained in the register will be
“backed off ” using ID 7.
CAUTION
Most manufacturers ship host bus adapters with a
default SCSI ID of 7. Ensure that the ID is
changed BEFORE you establish a connection
between the adapter and the Hub.
After all the IDs in the group have been serviced, a new group of IDs will be
captured at the next arbitration phase. The fair arbitration algorithm only applies
to host port SCSI IDs as defined by the assignment in each configuration.
CAUTION
Running the UltraSCSI Hub under heavy I/O with
Fair Arbritration disabled might result in SCSI Bus
starvation for hosts with lower SCSI IDs.
2.2 Large Hub Addressing Configurations
The large UltraSCSI Hub has a specific SCSI ID configuration. The SCSI IDs are
assigned to specific physical locations in the Hub. This allows the fair arbitration
logic in the Hub to correctly identify the SCSI IDs that are participating in a fair
arbitration cycle.
CAUTION
The SCSI ID of each host adapter must
correspond to the assigned SCSI ID of the host
port to which the host adapter is connected.
Mismatched SCSI IDs will cause the SCSI bus to
hang.
Figure 2-1 shows the physical layout of the ports and their associated SCSI ID
assignments.
2–2
EK–DWZZH–UG. D01
Chapter 2. Using the DWZZH UltraSCSI Hub
Figure 2–1 DWZZH–05 SCSI ID Assignments
C ontroller Port
SCSI ID 6-0
Host Port
SCSI ID 15
Host Port
SCSI ID 14
H ost Port
SCSI ID 13
Host Port
SCSI ID 12
S H R -1069
2.3 Narrow Addressing Setting
The large Hub can be used with SCSI bus architectures that are limited to eight
ID assignments, such as DIGITAL UNIX 4.x and earlier versions. (Figure 2-2
shows narrow ID assignments). The jumper on the rear of the Hub (Figure 2-3)
must be closed to make the Hub respond to SCSI IDs 3 – 0 on the host ports.
EK–DWZZH–UG. D01
2–3
DWZZH 16–Bit UltraSCSI Hub
Figure 2–2 DWZZH–05 SCSI Narrow ID Assignments
C ontroller Port
SCSI ID 6-4
Host Port
SCSI ID 3
Host Port
SCSI ID 2
Host Port
SCSI ID 1
Host Port
SCSI ID 0
S H R -1071
2–4
EK–DWZZH–UG. D01
Chapter 2. Using the DWZZH UltraSCSI Hub
Figure 2–3 DWZZH–05 SCSI Narrow Addressing Jumper
W1 (To enable narrow addressing mode, install a jumper at W1)
EK–DWZZH–UG. D01
2–5
DWZZH 16–Bit UltraSCSI Hub
2.4 Front Panel
Figure 2-4 shows the location of the front panel controls and indicators.
Figure 2–4 DWZZH–05 Front Panel
Fair
Disable
Power
Busy
S H R -1070
NOTE
The black part of the switch in the diagram
indicates the position of the switch.
2.4.1 Fair Arb Disable
The large Hub contains a switch on the front panel that allows the user to disable
the feature of the Hub. When is disabled, the Hub
FAIR ARB
FAIR ARB
services SCSI arbitration cycles in the conventional SCSI priority order. Host
port SCSI ID assignments are not linked to the physical port location in the Hub
when
is disabled.
FAIR ARB
2–6
EK–DWZZH–UG. D01
Chapter 2. Using the DWZZH UltraSCSI Hub
2.4.2 Indicators
The large Hub has two indicators on the front panel. The green LED indicates
that POWER is applied to the Hub, while the yellow LED indicates that the SCSI
bus is BUSY.
2.5 Determining the Configuration
The UltraSCSI Hub is used in end–bus SCSI bus configurations only. The SCSI
bus segments require TERMPOWER supplied from the remote connection to
enable the UltraSCSI Hub port for that segment. Each port on the UltraSCSI Hub
has its own terminators.
All SCSI buses are terminated at the physical ends of the bus. This is true even
when using a DWZZH UltraSCSI Hub. DWZZH UltraSCSI Hubs are factory set
to terminate the SCSI bus. No user configuration of the SCSI terminators is
required.
2.6 Selecting the SCSI Cables
The
, EK–ULTRA–CG,
StorageWorks UltraSCSI Configuration Guidelines
describes SCSI cables in detail. When selecting a cable you must consider the
cable connector clearance. Be sure to determine the type connector compatible
with the controller connector. In some cases you must use a right–angle
connector because there is not enough clearance to use a straight connector.
Cables connected to the DWZZH UltraSCSI Hubs are BN37A and BN38C series.
2.7 Placement of UltraSCSI Hubs
UltraSCSI Hubs are available only in SBBs and may be used only within a
BA356 StorageWorks shelf or a BA370 StorageWorks shelf. The StorageWorks
shelves are only used to provide power and cooling for UltraSCSI Hubs. An
UltraSCSI Hub and I/O devices may share the same storage shelf.
Maximum combinations of UltraSCSI Hubs and disk drives within a single shelf
and with dual power supplies are listed in Table 2-1.
EK–DWZZH–UG. D01
2–7
DWZZH 16–Bit UltraSCSI Hub
Table 2-1 Combinations of UltraSCSI Hubs and Devices in StorageWorks
Shelves
Number of
Small Hubs
(DWZZH–03/–21)
Number of
Large Hubs
(DWZZH–05)
Number of
Disk Drives
Personality
Module
5
4
3
2
1
0
3
2
1
0
0
0
0
0
0
2
1
1
1
1
0
0
3
4
5
0
0
1
2
3
Not installed
Installed
Installed
Installed
Installed
Not installed
Not installed
Installed
Installed
Installed
2–8
EK–DWZZH–UG. D01
3
SWCC and UltraSCSI Hubs
This chapter is intended to provide you with important information regarding the use of
StorageWorks Command Console on SCSI buses that have an UltraSCSI Hub. While
the information provided here is important, it is essential that you have read the SWCC
Manual and Release Notes.
3.1 Agents and Storage
It is highly recommended that you only run one SWCC agent on one of the
servers that can access a particular storage subsystem behind the DS-DWZZH-05
UltraSCSI Hub. Using SWCC through the client-agent model is very similar to
using a serial terminal to access the HSZ70 controller; running multiple agents to
access one storage subsystem would show up as multiple storage windows on the
SWCC-Client machine. This could be a potential problem, as the Client would
see multiple HSZ70 subsystems, when in fact, only one exists, but is being
displayed multiple times.
NOTE
If you have multiple storage subsystems behind
the DWZZH UltraSCSI Hub, be sure to name each
of your storage subsystems uniquely and carefully
(when you configure SWCC) so that you can
distinguish between them easily.
The SWCC Graphical User Interface (GUI) neither displays when HSZ access ID
restriction is being enforced nor prevents changes to restricted configurations
from the GUI. For example, consider having four servers, each with a uniquely
identified Host Bus Adapter attached to a DWZZH 5-port UltraSCSI Hub,
connected to an RA7000 subsystem (Figure 3–1). Furthermore, consider the case
where you have access ID restrictions configured such that each SCSI ID 12-15
could access a unique set of six disks in the storage cabinet.
EK–DWZZH–UG. D01
3–1
DWZZH 16-Bit UltraSCSI HUB
This type of configuration would prevent systems with different SCSI IDs from
accessing disks ‘
’ a particular SCSI ID, which promotes data
security between servers on a shared SCSI bus; however, it prevent
belonging to
does not
SWCC from performing tasks on those disks. In other words, if you set up the
SWCC client to have configuration capability (see SWCC documentation) then
you can access everything in the storage subsystem, regardless of HSZ70 access
ID restrictions.
For further information on setting up and configuring agents on HSZ controllers,
please see the SWCC and controller documentation.
3–2
EK–DWZZH–UG. D01
Chapter3. SWCC and UltraSCSI Hubs
Figure 3-1 Running One SWCC Agent for a Particular Storage Subsystem
BA370 Cabinet with HSZ70 Controllers
Host System
Host System
Agent
Host System
Host System
DWZZH–05
EK–DWZZH–UG. D01
3-3
Glossary
This Glossary includes an alphabetized listing and brief definition of the abbreviations,
acronyms, Compaq-specific references, and other technical terms that are used in this
manual and that may be unfamiliar to the reader.
adapter
See SCSI bus converter.
building block shelf
See SBB shelf.
controller
A hardware/firmware device that manages communications on behalf of host systems over the
SCSI bus to devices, such as the HSC-series, HSJ-series, and HSZ-series controllers. Controllers
typically differ by the type of interface to the host and provide functions beyond what the
devices support.
differential SCSI bus
A signal's level is determined by the potential difference between two wires. A differential bus
is more robust and less subject to electrical noise than is a single-ended bus.
DWZZC
A StorageWorks compatible 16-bit UltraSCSI bus converter.
See SCSI bus converter.
DWZZH
A StorageWorks compatible 16-bit UltraSCSI bus HUB.
electrostatic discharge
See ESD.
ESD
Electrostatic discharge is the discharge of a potentially harmful static electric voltage as a result
of improper grounding.
host
The primary or controlling computer or any such unit (in a multiple computer network) to which
storage is attached.
EK–DWZZH–UG. D01
Glossary–1
DWZZH 16–UltraSCSI Hub
host adapter
A device that connects the host system I/O bus (for example, a PCI bus) to the storage SCSI bus.
A host adapter performs the lower layers of the SCSI protocol and normally operates in the
initiator role.
initiator
A SCSI device that requests another device on the bus to perform an operation. Any device on
the bus can be an initiator or a target.
logical bus
A single-ended, or differential, physical bus connected to a differential, physical bus by a SCSI
bus converter.
personality module
The BA356 module that interfaces the SCSI-bus to the BA356 shelf.
physical bus
Two SCSI terminators separated by cables, connectors, and/or the backplane circuitry.
SBB
StorageWorks building block. The basic building block of the StorageWorks product line. Any
device conforming to shelf mechanical and electrical standards installed in either a 3½-inch or
5¼-inch carrier is considered to be an SBB, whether it is a storage device, a power supply, or
other device.
SBB shelf
The common name for any StorageWorks shelf that contains only power supply and storage
SBBs.
SCSI
Small Computer System Interface. This ANSI interface defines the physical and electrical
parameters of a parallel I/O bus used to connect computers and devices. The StorageWorks
subsystem implementation uses SCSI–2 or SCSI–3 for the transfer of data.
SCSI bus converter
Sometimes referred to as an adapter. (1) A connecting device that permits the attachment of
accessories or provides the capability to mount or link units. (2) The device that connects a
differential SCSI bus to a single-ended SCSI bus.
SCSI device
A host computer adapter, a peripheral controller, or an intelligent peripheral that can be attached
to the SCSI bus.
SCSI device ID
The bit-significant, representation of the SCSI addressing referring to one of the signal lines
numbered 0 through 15. Also referred to as target ID. For example, SCSI device ID 1 would be
represented as 00001.
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Glossay
SCSI end-bus position
The physical location of a controller or a device that contains the SCSI bus termination.
SCSI mid-bus position
The physical location of a controller or a device that the SCSI bus passes through enroute to the
controller or device that contains the SCSI bus termination.
SCSI cable
A 68-conductor (34 twisted pairs) cable used for differential bus connections.
single-ended SCSI bus
A bus in which each signal’s logic level is determined by the voltage of a single wire in relation
to ground.
Small Computer System Interface
See SCSI.
StorageWorks
The Digital set of enclosure products that allows customers to design and configure their own
storage subsystem. Components include power, packaging, and interconnections in a
StorageWorks shelf. SBBs and array controllers are integrated therein to form level enclosures
to house the shelves. Standard mounting devices for SBBs are also included.
StorageWorks building block
See SBB.
target
A SCSI device that performs an operation requested by an initiator. Any device on the bus can
be an initiator or a target.
target ID
See SCSI device ID.
terminators
The interconnect components that form the ends of the transmission lines in bus segments. A
SCSI domain must have at least one segment and therefore at least two terminators. The
terminators ensure that inactive SCSI bus signals are in a known state. There are two basic types
of terminators - active and passive.
•
•
Single-ended bus segments use active, linear terminators.
Differential bus segments use passive (linear totem pole) terminators.
except for special cases where the electrical transmission lines are very short and only one
termination or pull-up is required.
termpower
An electrical current that is limited by self-resetting fuses.
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UltraSCSI
An improvement in SCSI technology invented in 1993 by the Compaq Computer Corporation
StorageWorks Engineering Group. Subsequently the ANSI SCSI Standards Committee issued
standard X3T10 for UltraSCSI. The UltraSCSI improvements over Fast SCSI include the
following:
•
Maximum transfer rate increases from 10 MHz to 20 MHz.
VHDCI
Very High Density Cable Interconnect
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