Maximum Number Of Luns; Transfer Rates: Ultra, Fast, And Asynchronous; Wide And Narrow Scsi Buses - ADIC Scalar 100 User Manual

Maximum Number of LUNS

The ADIC Gateway supports up to 255 LUNS.
Attention: Do not attach more than 255 LUNS to the ADIC Gateway. Exceeding
the 255 LUN limit will result in unreliable behavior.

Transfer Rates: Ultra, Fast, and Asynchronous

The SCSI protocol defines two methods of data transfer: synchronous and
asynchronous. Asynchronous transfers may run as fast as 5 MHz, while
synchronous transfers may run as fast as 160 MHz (Ultra3).
The rate of transfer is negotiated between a SCSI initiator, such as the ADIC
Gateway, and each target. For each target device identified during a bus scan, the
ADIC Gateway will request a transfer rate at the fastest transfer rate supported by
the ADIC Gateway. The target will then reply with the maximum transfer rate it will
support.
Note: In general, devices that are capable of running at Ultra2/3 speeds should
not be mixed on a bus with slower devices, since the bus speed will be set to
match the slowest device on the bus.

Wide and Narrow SCSI Buses

A SCSI bus may be either narrow (8 bit) or wide (16 bit). The ADIC Gateway SCSI
buses are all wide, but may be connected to narrow devices with the correct cable
adapters.
Although it is possible to mix narrow and wide devices on a single SCSI bus, this
configuration is not recommended. If any of the devices supports Ultra2/3 speeds,
then a mix of narrow and wide devices is prohibited.
In order for the ADIC Gateway to locate and communicate with the devices, each
device on the SCSI bus must be assigned a unique target ID. On a wide (16 bit)
SCSI bus, the SCSI standard allows for a total of 16 target IDs. On a narrow (8 bit)
SCSI bus, the SCSI standard allows for a total of 8 target IDs. There are no
requirements about the ordering or position of the target IDs on the SCSI bus. The
only requirement is that there be no duplicate target IDs. By default, the ADIC
Gateway uses ID 7. Thus, peripheral devices may be assigned IDs 0 through 6
and 8 through 15, typically selected by a switch or jumpers. These settings may
be changed.
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Attention: Make sure you do not assign more than one device on a
bus to the same target ID. This will prevent that bus from working
properly.
ADIC Gateway Setup