 |
Michael Lampi President MDL Corporation |
 |
2667 170th Ave SE Bellevue, WA 98008-5516 USA Phone: (425) 861-6700 Fax: (425) 861-6767 E-mail: lampi at mdlcorp.com |
Description: Methods are provided by which one will be able to successfully configure SCSI devices and buses on HP systems. What attendees will learn: 1. Basic SCSI bus configurations and techniques. 2. How to add new LVD devices to your FWD systems. 3. How to properly extend and expand your Ultra SCSI buses to support more devices. Abstract: In the past two years HP has added a third flavor of SCSI bus (Ultra) to its line of workstations. During this time peripheral vendors have added a fourth flavor of SCSI (Ultra 2) to the mix and all but dropped one (Differential). This presentation discusses the options available for adding storage peripherals to a HP workstation. It includes a discussion of the limitations of each flavor of SCSI, and what can be done to expand the capabilities of legacy systems with narrow single ended, narrow fast differential and fast wide buses. It will also discuss how one can reliably expand systems with newer Ultra buses using Ultra or more advanced Ultra 2 LVD devices. New technology for creating high performance bus configurations will be presented. Several case studies will also shown. Biographical Sketch: For the past two decades Michael Lampi has been intimately involved with storage solutions for computer systems. For the past decade he has been involved with engineering and supporting high performance peripherals for Unix workstations. URL for this paper: http://www.mdlcorp.com
Basic Ingredients
Cables
| Narrow high density |  |
| Narrow low density, also known as Centronics | |
| Wide high density |
Operating System Software
SCSI Peripherals
Disk drives
Tape drives
CD-ROM
RAID
Terminators
| Passive |  |
| Active | |
| Active Negation | |
| Forced Perfect | |
| LVD, also known as Low Voltage Differential | |
| Differential |
Workstation Host SCSI Adapters
Core Slow Single Ended Narrow
Core Ultra-1 Single Ended
Core Fast Wide (Differential) Wide
EISA Fast Single Ended
EISA Fast Differential
PCI Single Ended
PCI Differential
PCI LVD
Spices
Wide to Narrow Converters
Single Ended to LVD Converters
Single Ended to Differential Converters
Ultra-1 Bus Signal Boosters
Semi-Terminating Cables
Basic Concepts
1. In all cases a SCSI bus must start with a terminator at one end and end with a terminator at the other end. There must be no other terminators in a single SCSI bus. Remember that HP workstations normally provide the termination of one of the ends of the bus.
2. In all cases the SCSI addresses of each device on a SCSI bus must be distinct and different from each other. Remember that HP workstations normally reserve SCSI address 7 for their use.
3. The total cable length of a single SCSI bus must be within the limits for that particular type of SCSI bus. Do not try to use 20 meter cables to connect two Ultra-1 single ended devices together.
4. The type of SCSI terminators used must be compatible with the type of SCSI bus. This means that you should use low voltage differential (LVD) terminators with LVD buses. Differential terminators are used with differential buses. Active negation terminators are used with Ultra-1 single ended buses. Forced perfect or active terminators are used with fast single ended buses and passive terminators are used with slow single ended SCSI buses.
5. The SCSI peripherals to be added must be compatible with the electrical type of SCSI bus being used. This means that you can not mix differential and LVD devices, or differential and single ended devices.
6. LVD devices can operate as Single Ended devices when used on a Single Ended bus. However, the penalty for doing this is that these devices are subject to the same limitations as any other single ended device on that bus. Also, placing a single ended device on a LVD bus causes the entire bus to convert to the Single Ended mode of operation.
7. HP mislabeled the fast wide differential SCSI connectors on their Series 700 and C series boxes for years as "Fast Wide SCSI". Only differential devices can be connected to this bus.
8. EISA and PCI SCSI adapters can be added to most workstations in order to provide additional buses.
9. Be aware that the connector pins in high density connectors are easily bent. Take care when plugging them in!
Be sure that you can properly identify the electrical type(s) of buses you have on your system!
Older Workstation Recipes
These recipes are oriented for our mature audience. In particular, these work well with HP 9000 Series 700 workstations. Some of the younger systems will also find these palatable.
You will find that adding a SCSI peripheral will always involve these basic recipes, so it is advisable to check them out before trying one of the more advanced ones.
Adding a Disk Drive to the Core Single Ended SCSI bus
This is a fairly standard recipe, and can be applied to newer audiences as well with much success. Here we will add a disk drive to the Core Single Ended Slow SCSI bus.
| Ingredients: |
|
|
| 1 | External cabinet with a Single Ended disk drive | |
| 1 | Workstation with no external peripherals | |
| 1 | SCSI cable with a high density narrow (50 pin) connector at one end, and a connector appropriate for the external cabinet. This is typically either a high density narrow (50 pin) connector, or a low density narrow (50 pin) connector. Remember, the total cable length must be less than 5 meters. The shorter the better! | |
| 1 | Terminator, single ended (any type), with a connector that matches that on the cabinet. | |
| Optional: | ||
| 1 | Power strip | |
Log into the workstation as the super user, e.g., root.
Now we find the addresses used on your workstation for SCSI devices.
Run ioscan –f
The results should be similar to the following from a 720 workstation:
root[1]//harpo/users/root# ioscan -f Class I H/W Path Driver S/W State H/W Type Description ============================================================================ bc 0 root CLAIMED BUS_NEXUS graphics 0 1 graph3 CLAIMED INTERFACE Graphics ba 0 2 bus_adapter CLAIMED BUS_NEXUS Core I/O Adapter ext_bus 0 2/0/1 c720 CLAIMED INTERFACE Built-in SCSI target 1 2/0/1.6 tgt CLAIMED DEVICE disk 0 2/0/1.6.0 sdisk CLAIMED DEVICE FUJITSU M2654S-512 target 0 2/0/1.7 tgt CLAIMED DEVICE ctl 0 2/0/1.7.0 sctl CLAIMED DEVICE Initiator lan 0 2/0/2 lan2 CLAIMED INTERFACE Built-in LAN hil 0 2/0/3 hil CLAIMED INTERFACE Built-in HIL tty 0 2/0/4 asio0 CLAIMED INTERFACE Built-in RS-232C tty 1 2/0/5 asio0 CLAIMED INTERFACE Built-in RS-232C ext_bus 1 2/0/6 CentIf CLAIMED INTERFACE Built-in Parallel Interface ba 1 4 eisa CLAIMED BUS_NEXUS EISA Adapter processor 0 8 processor CLAIMED PROCESSOR Processor memory 0 9 memory CLAIMED MEMORY Memory
Notice the "Class" column. Scan down it until you find entry labeled "ba", which stands for "bus adapter".
Also notice that this has the description "Core I/O Adapter". This is close to the entry we want. Look at the next entry labeled "ext_bus", and "Built-in SCSI". Check on the following lines for "target" entries. The last digit in the "H/W Path" column of information shows which addresses are currently in use. In the example above the entries we are interested in have "2/0/1.6" and "2/0/1.7". These correspond to SCSI bus addresses 6 and 7. These are addresses that we must avoid when setting the SCSI address of the external disk drive.
Set the SCSI address of the external disk drive. Let's try using address 1.
Shut down and power off the workstation.
Make sure that the power switch on the external cabinet is in the OFF position.
At this time, if you have the optional power strip, plug the workstation, monitor and external cabinet into the power strip. Plug the power strip into the power outlet. Otherwise, just plug the external cabinet into the power outlet.
Locate the Core SE SCSI bus connector on the workstation. It should have a short, stubby terminator plugged into it. Note that on some workstations there might not be an external terminator.
Plug the cable into the workstation and into the external cabinet. Note that each connector on the cable is keyed so that it will fit only one way, and only into the proper connector on the workstation.
Plug the terminator into the other connector on the external cabinet.
Check each connector to make sure that it is fully seated and properly secured.
At this time you should apply power, first to the workstation and then to the disk drive. If you have the optional power strip turn the power strip off. Turn the power switches on the workstation and the external cabinet on. Finally, turn on the power strip.
Log into the system as root.
Run ioscan –f
The results should be similar to the following:
root[1]//harpo/users/root# ioscan -f Class I H/W Path Driver S/W State H/W Type Description ============================================================================ bc 0 root CLAIMED BUS_NEXUS graphics 0 1 graph3 CLAIMED INTERFACE Graphics ba 0 2 bus_adapter CLAIMED BUS_NEXUS Core I/O Adapter ext_bus 0 2/0/1 c720 CLAIMED INTERFACE Built-in SCSI target 2 2/0/1.1 tgt CLAIMED DEVICE disk 1 2/0/1.1.0 sdisk CLAIMED DEVICE SEAGATE ST15230N target 1 2/0/1.6 tgt CLAIMED DEVICE disk 0 2/0/1.6.0 sdisk CLAIMED DEVICE FUJITSU M2654S-512 target 0 2/0/1.7 tgt CLAIMED DEVICE ctl 0 2/0/1.7.0 sctl CLAIMED DEVICE Initiator lan 0 2/0/2 lan2 CLAIMED INTERFACE Built-in LAN hil 0 2/0/3 hil CLAIMED INTERFACE Built-in HIL tty 0 2/0/4 asio0 CLAIMED INTERFACE Built-in RS-232C tty 1 2/0/5 asio0 CLAIMED INTERFACE Built-in RS-232C ext_bus 1 2/0/6 CentIf CLAIMED INTERFACE Built-in Parallel Interface ba 1 4 eisa CLAIMED BUS_NEXUS EISA Adapter processor 0 8 processor CLAIMED PROCESSOR Processor memory 0 9 memory CLAIMED MEMORY Memory
As you can see from the above information, the workstation now has a new disk drive at SCSI address 1.
Under HP-UX 10.00 and above the character and block device special files are automatically created at boot time. Running the command "dmesg" will display the names of these device files.
The Logical Volume Manager can be used to configure this drive prior to placing a file system on this drive. System utility programs, such as sam, newfs and mkfs, can now be used to create a file system on the disk drive.
Congratulations! You have successfully added a SCSI peripheral to your workstation.
For a variation on the above recipe, you can add a tape drive, CD-ROM drive, or any other SCSI peripheral.
For another variation on the above recipe, you can add a peripheral to a bus that already has another SCSI device connected to it:
Adding a Disk Drive to the Core Fast Wide (Differential) SCSI bus
This is a fairly standard recipe, and can be applied to newer audiences as well with much success. Here we will add a disk drive to the Core Fast Wide Differential SCSI bus.
| Ingredients: |
|
|
| 1 | External cabinet with a Differential Wide disk drive | |
| 1 | Workstation with no external peripherals | |
| 1 | SCSI cable with a high density wide (68 pin) connector at each end. | |
| 1 | Terminator, differential, with a high density wide (68 pin) connector. | |
| Optional: | ||
| 1 | Power strip | |
Log into the workstation as the super user, e.g., root.
Now we find the addresses used on your workstation for SCSI devices.
Run ioscan –f
The results should be similar to the following from a C160 workstation:
root[1]//zippo/users/root# ioscan -f Class I H/W Path Driver S/W State H/W Type Description ======================================================================= bc 0 root CLAIMED BUS_NEXUS bc 1 8 ccio CLAIMED BUS_NEXUS I/O Adapter unknown -1 8/0 UNCLAIMED UNKNOWN GSC-to-PCI Bus Bridge ext_bus 0 8/12 c720 CLAIMED INTERFACE GSC Fast/Wide SCSI Interface target 0 8/12.6 tgt CLAIMED DEVICE disk 0 8/12.6.0 sdisk CLAIMED DEVICE SEAGATE ST32430W target 1 8/12.7 tgt CLAIMED DEVICE ctl 0 8/12.7.0 sctl CLAIMED DEVICE Initiator ba 0 8/16 bus_adapter CLAIMED BUS_NEXUS Core I/O Adapter ext_bus 2 8/16/0 CentIf CLAIMED INTERFACE Built-in Parallel Interface audio 0 8/16/1 audio CLAIMED INTERFACE Built-in Audio tty 0 8/16/4 asio0 CLAIMED INTERFACE Built-in RS-232C ext_bus 1 8/16/5 c720 CLAIMED INTERFACE Built-in SCSI target 2 8/16/5.7 tgt CLAIMED DEVICE ctl 1 8/16/5.7.0 sctl CLAIMED DEVICE Initiator lan 0 8/16/6 lan2 CLAIMED INTERFACE Built-in LAN ps2 0 8/16/7 ps2 CLAIMED INTERFACE Built-in Keyboard/Mouse ba 1 8/20 bus_adapter CLAIMED BUS_NEXUS Core I/O Adapter hil 0 8/20/1 hil CLAIMED INTERFACE Built-in HIL tty 1 8/20/2 asio0 CLAIMED INTERFACE Built-in RS-232C ba 2 8/20/5 eisa CLAIMED BUS_NEXUS EISA Bus Adapter graphics 0 8/24 graph3 CLAIMED INTERFACE Graphics bc 2 10 ccio CLAIMED BUS_NEXUS I/O Adapter graphics 1 10/12 graph3 CLAIMED INTERFACE Graphics processor 0 32 processor CLAIMED PROCESSOR Processor memory 0 49 memory CLAIMED MEMORY Memory
Notice the "Class" column. Scan down it until you find entry "ext_bus", and "GSC Fast/Wide SCSI Interface". Check on the following lines for "target" entries. The last digit in the "H/W Path" column of information shows which addresses are currently in use. In the example above the entries we are interested in have "8/12.6" and "8/12.7". These correspond to SCSI bus addresses 6 and 7. These are addresses that we must avoid when setting the SCSI address of the external disk drive.
Set the SCSI address of the external disk drive. Let's try using address 1.
Shut down and power off the workstation.
Make sure that the power switch on the external cabinet is in the OFF position.
At this time, if you have the optional power strip, plug the workstation, monitor and external cabinet into the power strip. Plug the power strip into the power outlet. Otherwise, just plug the external cabinet into the power outlet.
Locate the Core FW SCSI bus connector on the workstation. It should have a short, wide stubby terminator plugged into it. Note that on some workstations there might not be an external terminator.
Plug the cable into the workstation and into the external cabinet. Note that each connector on the cable is keyed so that it will fit only one way, and only into the proper connector on the workstation.
Plug the terminator into the other connector on the external cabinet.
Check each connector to make sure that it is fully seated and properly secured.
At this time you should apply power, first to the workstation and then to the disk drive. If you have the optional power strip turn the power strip off. Turn the power switches on the workstation and the external cabinet on. Finally, turn on the power strip.
Log into the system as root.
Run ioscan –f
The results should be similar to the following:
root[1]//zippo/users/root# ioscan -f Class I H/W Path Driver S/W State H/W Type Description ======================================================================= bc 0 root CLAIMED BUS_NEXUS bc 1 8 ccio CLAIMED BUS_NEXUS I/O Adapter unknown -1 8/0 UNCLAIMED UNKNOWN GSC-to-PCI Bus Bridge ext_bus 0 8/12 c720 CLAIMED INTERFACE GSC Fast/Wide SCSI Interface target 3 8/12.1 tgt CLAIMED DEVICE disk 1 8/12.1.0 sdisk CLAIMED DEVICE SEAGATE ST32430W target 0 8/12.6 tgt CLAIMED DEVICE disk 0 8/12.6.0 sdisk CLAIMED DEVICE SEAGATE ST32430W target 1 8/12.7 tgt CLAIMED DEVICE ctl 0 8/12.7.0 sctl CLAIMED DEVICE Initiator ba 0 8/16 bus_adapter CLAIMED BUS_NEXUS Core I/O Adapter ext_bus 2 8/16/0 CentIf CLAIMED INTERFACE Built-in Parallel Interface audio 0 8/16/1 audio CLAIMED INTERFACE Built-in Audio tty 0 8/16/4 asio0 CLAIMED INTERFACE Built-in RS-232C ext_bus 1 8/16/5 c720 CLAIMED INTERFACE Built-in SCSI target 2 8/16/5.7 tgt CLAIMED DEVICE ctl 1 8/16/5.7.0 sctl CLAIMED DEVICE Initiator lan 0 8/16/6 lan2 CLAIMED INTERFACE Built-in LAN ps2 0 8/16/7 ps2 CLAIMED INTERFACE Built-in Keyboard/Mouse ba 1 8/20 bus_adapter CLAIMED BUS_NEXUS Core I/O Adapter hil 0 8/20/1 hil CLAIMED INTERFACE Built-in HIL tty 1 8/20/2 asio0 CLAIMED INTERFACE Built-in RS-232C ba 2 8/20/5 eisa CLAIMED BUS_NEXUS EISA Bus Adapter graphics 0 8/24 graph3 CLAIMED INTERFACE Graphics bc 2 10 ccio CLAIMED BUS_NEXUS I/O Adapter graphics 1 10/12 graph3 CLAIMED INTERFACE Graphics processor 0 32 processor CLAIMED PROCESSOR Processor memory 0 49 memory CLAIMED MEMORY Memory
As you can see from the above information, the workstation now has a new disk drive at SCSI address 1.
Under HP-UX 10.00 and above the character and block device special files are automatically created at boot time. Running the command "dmesg" will display the names of these device files.
The Logical Volume Manager can be used to configure this drive prior to placing a file system on this drive. System utility programs, such as sam, newfs and mkfs, can now be used to create a file system on the disk drive.
Congratulations! You have successfully added a wide differential SCSI peripheral to your workstation.
For a variation on the above recipe, you can add a wide differential tape drive, a RAID system or any other wide differential SCSI peripheral.
Adding a Disk Drive to an EISA SCSI Adapter
This is somewhat more exotic than the standard fare, and can only be applied to systems with EISA or PCI SCSI adapters. Here we will add a disk drive to an EISA Fast Wide Differential SCSI Adapter SCSI bus.
| Ingredients: |
|
|
| 1 | External cabinet with a Wide Differential disk drive | |
| 1 | Workstation with an EISA Wide Differential SCSI adapter board | |
| 1 | SCSI cable with a high density wide (68 pin) connector at both ends | |
| 1 | Terminator, differential type, with a high density wide (68 pin) connector | |
| Optional: | ||
| 1 | Power strip | |
Log into the workstation as the super user, e.g., root.
Now we find the addresses used on your workstation for SCSI devices.
Run ioscan –f
The results should be similar to the following:
root[1]//harpo/users/root# ioscan -f Class I H/W Path Driver S/W State H/W Type Description ============================================================================ bc 0 root CLAIMED BUS_NEXUS graphics 0 1 graph3 CLAIMED INTERFACE Graphics ba 0 2 bus_adapter CLAIMED BUS_NEXUS Core I/O Adapter ext_bus 0 2/0/1 c720 CLAIMED INTERFACE Built-in SCSI target 0 2/0/1.6 tgt CLAIMED DEVICE disk 0 2/0/1.6.0 sdisk CLAIMED DEVICE FUJITSU M2654S-512 target 1 2/0/1.7 tgt CLAIMED DEVICE ctl 0 2/0/1.7.0 sctl CLAIMED DEVICE Initiator lan 0 2/0/2 lan2 CLAIMED INTERFACE Built-in LAN hil 0 2/0/3 hil CLAIMED INTERFACE Built-in HIL tty 0 2/0/4 asio0 CLAIMED INTERFACE Built-in RS-232C tty 1 2/0/5 asio0 CLAIMED INTERFACE Built-in RS-232C ext_bus 1 2/0/6 CentIf CLAIMED INTERFACE Built-in Parallel Interface ba 1 4 eisa CLAIMED BUS_NEXUS EISA Adapter ext_bus 2 4/0/1 faws CLAIMED INTERFACE EISA card BUS4202 unknown -1 4/0/1.7 UNCLAIMED UNKNOWN FAWS firmware rev. 429Dx target 2 4/0/1.8 tgt CLAIMED DEVICE disk 1 4/0/1.8.0 sdisk CLAIMED DEVICE HP C2490WD processor 0 8 processor CLAIMED PROCESSOR Processor memory 0 9 memory CLAIMED MEMORY Memory
As before, scan down the "Class" column until you find entry labeled "ba", which stands for "bus adapter". As you notice on the next lines this information relates to the built-in SCSI, which is not the EISA bus adapter that we wish to connect with our new disk drive.
Scan further down the "Class" column for the next "ba" entry. Notice that it contains a description with "EISA Adapter". This is close to what we want. Look for the next entry labeled "ext_bus". If this is labeled with some identifiable SCSI bus adapter, then we have found our hardware path. Otherwise, keep searching.
Check on the following lines for "target" entries. The last digit in the "H/W Path" column of information shows which addresses are currently in use. In the example above the entries we are interested in have "4/0/1.7" through "4/0/1.8". These correspond to SCSI bus addresses 7 and 8. These are addresses that we must avoid when setting the SCSI address of the new external disk drive.
Set the SCSI ID of the new external cabinet to some other number, such as 6.
As before, shut down and power off the workstation and all external devices connected to the system.
Locate the EISA SCSI adapter. EISA adapters look very similar to IBM PC clone circuit boards, and HP workstations typically have one or more slots into which such a board could be installed.
Once the EISA SCSI adapter board has been found trace you can connect the new external cabinet directly to it. If there are other devices already connected, as in our example, you can choose to connect the new cabinet to the last external device cabled to the EISA SCSI adapter. You can potentially connect the new device in the middle of the previous devices as well. Just make sure that the SCSI cable from the EISA SCSI adapter is connected to the first device, the cable from the first device is connected to the second device, etc., and that the last device has both a SCSI cable connected to it as well as the terminator.
Check each connector to make sure that it is fully seated and properly secured.
At this time you should apply power, first to the workstation and then to the disk drive. If you have the optional power strip turn the power strip off. Turn the power switches on the workstation and the external cabinet on. Finally, turn on the power strip.
Log into the system as root.
Run ioscan –f
The results should be similar to the following:
root[1]//harpo/users/root# ioscan -f Class I H/W Path Driver S/W State H/W Type Description ============================================================================ bc 0 root CLAIMED BUS_NEXUS graphics 0 1 graph3 CLAIMED INTERFACE Graphics ba 0 2 bus_adapter CLAIMED BUS_NEXUS Core I/O Adapter ext_bus 0 2/0/1 c720 CLAIMED INTERFACE Built-in SCSI target 0 2/0/1.6 tgt CLAIMED DEVICE disk 0 2/0/1.6.0 sdisk CLAIMED DEVICE FUJITSU M2654S-512 target 1 2/0/1.7 tgt CLAIMED DEVICE ctl 0 2/0/1.7.0 sctl CLAIMED DEVICE Initiator lan 0 2/0/2 lan2 CLAIMED INTERFACE Built-in LAN hil 0 2/0/3 hil CLAIMED INTERFACE Built-in HIL tty 0 2/0/4 asio0 CLAIMED INTERFACE Built-in RS-232C tty 1 2/0/5 asio0 CLAIMED INTERFACE Built-in RS-232C ext_bus 1 2/0/6 CentIf CLAIMED INTERFACE Built-in Parallel Interface ba 1 4 eisa CLAIMED BUS_NEXUS EISA Adapter ext_bus 2 4/0/1 faws CLAIMED INTERFACE EISA card BUS4202 target 3 4/0/1.1 tgt CLAIMED DEVICE disk 2 4/0/1.1.0 sdisk CLAIMED DEVICE HP C2490WD unknown -1 4/0/1.7 UNCLAIMED UNKNOWN FAWS firmware rev. 429Dx target 2 4/0/1.8 tgt CLAIMED DEVICE disk 1 4/0/1.8.0 sdisk CLAIMED DEVICE HP C2490WD processor 0 8 processor CLAIMED PROCESSOR Processor memory 0 9 memory CLAIMED MEMORY Memory
As you can see from the above information, the workstation now has a new disk drive at SCSI address 1.
Under HP-UX 10.00 and above the character and block device special files are automatically created at boot time. Running the command "dmesg" will display the names of these device files.
The Logical Volume Manager can be used to configure this drive prior to placing a file system on this drive. System utility programs, such as sam, newfs and mkfs, can now be used to create a file system on the disk drive.
Congratulations! You have successfully added a SCSI peripheral to your workstation's EISA SCSI adapter.
For a variation on the above recipe, if your EISA SCSI adapter is narrow differential, then the cable connectors would all be of the 50 conductor variety.
For another variation on the above recipe, if your EISA SCSI adapter is single ended, then the terminators would be of the Active, Forced Perfect or Active Negation variety.
Newer Workstation Recipes
These recipes are oriented for a younger audience. In particular, these are intended for systems with Ultra-1 SCSI interfaces.
Adding a Disk Drive to the Core Single Ended Ultra-1 SCSI bus
This is a very standard recipe, and is pretty much a duplicate of one in the Older Workstation Recipe section. Here we will add a disk drive to the Core Single Ended Ultra-1 SCSI bus.
| Ingredients: |
|
|
| 1 | External cabinet with a Single Ended disk drive | |
| 1 | Workstation with no external peripherals | |
| 1 | Short (less than 2 foot) SCSI cable with a high density wide (68 pin) connector at each end | |
| 1 | Terminator, single ended wide (68 pin) Active Negation | |
| Optional: | ||
| 1 | Power strip | |
The remaining steps are identical to those for adding a drive to an older workstation.
The critical points are to make sure that the SCSI bus cable lengths are kept to a minimum. Three foot (1 meter) cables are too long to connect the workstation to the external device.
It is not recommended that more than a single external device is connected to the Ultra-1 SCSI bus if any of the devices are to operate properly at Ultra-1 SCSI transfer rates.
For a variation on the above recipe, you can add a tape drive, CD-ROM drive, or any other SCSI peripheral.
Adding Several Disk Drive to the Core Single Ended Ultra-1 SCSI bus
This explores an area that is relatively new to the HP workstation audience. Since the Ultra-1 SCSI bus has quite stringent cable length limitations, yet is the fastest I/O bus on the system, it is quite attractive to add as much high performance capacity to this bus as possible.
How can this be done?
There are several answers to this problem, and they all have a similar basis. That is, terminate the host Ultra-1 bus as soon as possible, and link it to a new SCSI bus segment. Optionally, instead of multiple external devices, a RAID system could be directly connected to the host bus.
The new SCSI bus segment can be another Ultra-1 Single Ended bus, an Ultra-1 differential bus, or an Ultra-1 speed low voltage differential bus. Note that while this new bus segment is electrically isolated from the original bus the SCSI addresses are preserved.
Here we will add a disk drive to the Core Single Ended Ultra-1 SCSI bus.
| Ingredients: |
|
|
| 1 | External cabinet with one to four Single Ended disk drives | |
| 1 | Workstation with no external peripherals | |
| 1 | Ultra-1 wide (68 pin) SCSI bus booster | |
| 1 | Short (less than 2 foot) SCSI cable with a high density wide (68 pin) connector at each end | |
| 1 | Terminator, single ended wide (68 pin) Active Negation | |
| Optional: | ||
| 1 | Power strip | |
The first steps, which include determining an unused SCSI address, setting the address of the new disk drive, and removing power from the workstation, are the same as in the other recipes.
The critical point is to connect a short SCSI cable between the workstation Ultra-1 SCSI bus port and the SCSI bus booster. There is no external terminator on either end of this cable. The pass-through Ultra-1 booster internally terminates both segments.
Connect the second short SCSI cable from the other connector on the booster to one of the connectors on the external disk drive cabinet. Connect the active negation terminator to the other connector on the external disk drive cabinet.
It is not recommended that more than three external devices, in the same single cabinet, are connected to the Ultra-1 SCSI bus if any of the devices are to operate properly at Ultra-1 SCSI transfer rates.
The remaining steps are identical to those for adding a drive to an older workstation.
For a variation on the above recipe, you can replace the Ultra-1 SCSI booster with an Ultra-1 differential converter. This enables you to extend the bus length up to 12 meters when used with high voltage differential devices.
For another variation on the above recipe, you can replace the Ultra-1 SCSI booster with an Ultra-1 LVD converter. This enables you to extend the bus length up to 12 meters when used with low voltage differential devices, which are becoming much more readily available these days.
For yet another variation on the above recipe, you can replace the Ultra-1 SCSI pass-through booster with an Ultra-1 SCSI three-way booster. This enables you to tap onto the original bus without terminating it, yet provide an Ultra-1 bus segment for up to four devices. The original bus can continue on to another device, or another Ultra-1 SCSI pass-through booster.
Appendix
Standard Cable Length Limitations
| Single Ended | Differential | |
| SCSI-1 | 6 meters | 25 meters |
| SCSI-2 | 6 meters | 25 meters |
| SCSI-2 fast | 3 meters | 25 meters |
| SCSI-2 ultra | 1.5 meters | 12 meters |
| SCSI-2 ultra-2 | -- | 12 meters |
| SCSI Ultra160/m | -- | 12 meters |
Maximum Transfer Speeds
Megabytes/second
| Narrow | Wide | |
| SCSI-1 | less than 5 | -- |
| SCSI-2 | up to 5 | up to 10 |
| SCSI-2 fast | up to 10 | up to 20 |
| SCSI-2 ultra | up to 20 | up to 40 |
| SCSI-2 ultra-2 | up to 40 | up to 80 |
| SCSI Ultra160/m | up to 80 | up to 160 |
References
An excellent source of questions and answers from comp.periphs.scsi, and a rather humorous set of rules: http://fieldnet.ne.mediaone.net/gary/scsi.html
A variety of white papers discussing the various virtues of the various flavors of SCSI and Fibre Channel:
http://www.quantum.com/src/whitepapers/ultra2_TIP.html
http://www.quantum.com/src/whitepapers/ultraSCSI.html
http://www.quantum.com/src/whitepapers/fibre/
Miscellaneous useful SCSI sites:
http://www.bandwidth.net/scsi.html
http://www.adaptec.com/support/files/miscellaneous.html
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