Compaq Computer Accessories DWZZH User Manual

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.  
Glossary–2  
EK–DWZZH–UG. D01  
 
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.  
EK–DWZZH–UG. D01  
Glossary–3  
 
DWZZH 16–UltraSCSI Hub  
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  
Glossary–4  
EK–DWZZH–UG. D01  
 

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