HP Workstation xw6000 Adaptec SCSI RAID 2120S: Installation Guide - Page 21

LVD and SE Devices, Narrow and Wide SCSI Devices

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Adaptec SCSI RAID 2120S/2200S Installation Guide LVD and SE Devices Use of Ultra 2 or later drives is recommended. Ultra 2 was the first SCSI specification using Low Voltage Differential (LVD) signaling, use of LVD devices is recommended for creating arrays. Singleended (SE) devices function with the Adaptec SCSI RAID 2120S/ 2200S controllers. If attached, however, an SE SCSI device will cause the channel to slow to Ultra SCSI speed (20 MHz) or less for all devices. Other limitations and configuration challenges may ensue from use of SE devices. When using the controller to create arrays, keep all of your high performance devices on the same channel. See Mixing Devices on a Channel later in this chapter for more information. Narrow and Wide SCSI Devices You can attach either narrow (8-bit) or wide (16-bit) SCSI devices to your Adaptec SCSI controller. If using narrow and wide devices on the same wide cable, use a cable with an attached terminator or put one of the wide devices at the end of the cable. This ensures that the 16-bit signals are correctly terminated. See the following section for more details and diagrams that may be helpful. Note: To ensure proper termination, use the supplied cable or one like it, having a multimode terminator built in, and disable termination on all attached devices to that cable. LVD devices do not offer termination and must be used with a cable of this type. Wide devices allow data to be transferred at twice the rate of narrow devices of the same rating. The wide channel is backward compatible with narrow devices, allowing both types of SCSI devices to be used with the same controller. The narrow interface is still used with some SCSI devices, such as tape and CD-ROM drives. 2-2

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2-2
Adaptec SCSI RAID 2120S/2200S Installation Guide
LVD and SE Devices
Use of Ultra 2 or later drives is recommended. Ultra 2 was the first
SCSI specification using Low Voltage Differential (LVD) signaling,
use of LVD devices is recommended for creating arrays. Single-
ended (SE) devices function with the Adaptec SCSI RAID 2120S/
2200S controllers. If attached, however, an SE SCSI device will
cause the channel to slow to Ultra SCSI speed (20 MHz) or less for
all devices. Other limitations and configuration challenges may
ensue from use of SE devices.
When using the controller to create arrays, keep all of your high
performance devices on the same channel. See
Mixing Devices on a
Channel
later in this chapter for more information.
Narrow and Wide SCSI Devices
You can attach either narrow (8-bit) or wide (16-bit) SCSI devices to
your Adaptec SCSI controller. If using narrow and wide devices on
the same wide cable, use a cable with an attached terminator or put
one of the wide devices at the end of the cable. This ensures that the
16-bit signals are correctly terminated. See the following section for
more details and diagrams that may be helpful.
Note:
To ensure proper termination, use the supplied cable or
one like it, having a multimode terminator built in, and
disable termination on all attached devices to that cable. LVD
devices do not offer termination and must be used with a
cable of this type.
Wide devices allow data to be transferred at twice the rate of
narrow devices of the same rating. The wide channel is backward
compatible with narrow devices, allowing both types of SCSI
devices to be used with the same controller. The narrow interface is
still used with some SCSI devices, such as tape and CD-ROM
drives.