Appendix D: Ultrascsi Limitations - ATTO Technology SCSI Sidekick User Manual

A D: U
PPENDIX
Due to the electrical noise incurred with high-speed data transfer rates, UltraSCSI has
cabling and device limitations. ATTO SCSI Sidekick was engineered to address this
issue. Using a ATTO SCSI Sidekick in your configuration will help eliminate the cabling
and device limitations.
Table D-1 explains the maximum number of devices you may use relative to your cable
distance. For example, take the single-ended distance in an UltraSCSI environment
(Cells 3 & 4 in the single-ended bus length column). Look at the corresponding cells in
the maximum devices column to determine the maximum number of devices you may
connect at the specific distance. In an UltraSCSI environment, using a single-ended bus
length of 3 meters, you can only connect 4 devices. Using a single-ended bus length of
1.5 meters, you can connect up to 8 devices.
SCSI Type
Fast SCSI
Fast/WIDE SCSI
UltraSCSI
UltraSCSI
Ultra/WIDE SCSI
Ultra/WIDE SCSI
Ultra2/WIDE SCSI
Table D-1: UltraSCSI Cabling and Device Limitations
Table D-1 lists the maximum number of devices you may connect at specific cable
distances using differential and single-ended SCSI in various SCSI environments.
In an UltraSCSI workgroup environment with a 7-drive tower, you are limited to 1.5
meters between the host and the tower (this distance includes the cabling for the tower).
For example, if the 7-drive tower requires 1 meter of cabling to connect all of its drives,
the distance from the tower to the host would be .5 meters. Adding an ATTO SCSI
Sidekick to this configuration would increase the distance between the host and tower to 2
meters.
Please note that UltraSCSI is very sensitive to SCSI bus noise, cable distances, and the
number of devices connected on the SCSI bus. Be cautious when working with UltraSCSI
by carefully connecting your devices. Use Table D-1 to assist you when attempting to
configure your workgroup. If you have any questions or issues occur with your
configuration, please call an ATTO technical support representative.
ATTO SCSI Sidekick (USUS/UDUS) User's Manual
SCSI L
LTRA
Single-Ended
Bus Length
3 Meters
3 Meters
1.5 Meters
3 Meters
N/A
1.5 Meters
3 Meters
IMITATIONS
Differential
25 Meters
25 Meters
25 Meters
N/A
25 Meters
N/A
N/A
Maximum Devices
8
16
8
4
16
8
4
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