HP Workstation xw6000 Adaptec SCSI RAID 2120S: Installation Guide - Page 22

Mixing Devices on a Channel, Differential HVD interface

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Installing The Controller Mixing Devices on a Channel There are numerous types of SCSI devices on the market, and it may be tempting to mix state-of-the-art devices with others that may be available. While most combinations will work, performance will be degraded. Adaptec Ultra320 RAID controllers are meant to be used to construct arrays using Ultra320 drives and Ultra320 cables. Mixing any other type of device or cable with Ultra320 devices may reduce the performance on that channel. The Adaptec SCSI RAID controllers may be used in LVD mode or SE mode. To operate at their maximum designed rate, LVD devices must be connected only with LVD devices on a channel. The cable used with LVD devices must supply the termination, since LVD devices do not provide termination. LVD devices will automatically connect as SE if any SE only device is connected to that channel. ! Caution: If you have older SCSI-2 devices with a High Voltage Differential (HVD) interface, DO NOT USE THEM with the Adaptec SCSI RAID controller. Doing so will damage the controller. Use of Ultra 2 devices will reduce the performance dramatically! Other LVD devices attached typically won't impact the performance of Ultra320 devices on the same channel, although the maximum transfer rate of each LVD device will be limited to that device's native design speed. If SCSI devices other than LVD interfaced hard disk drives (SE) have to be attached to your system, they are best connected either to a separate SCSI controller, or a channel of the RAID controller not used by any arrays. This is due to the SE devices limiting the transfer rate of all devices attached to that channel. SE specifications allow for maximum connecting cable lengths of either 1.5 m or 3 m, depending on transfer speed. This alone could make the addition of an SE device to a working system not function if the system was operating in LVD mode and using longer cable lengths as allowed by later versions of SCSI. 2-3

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2-3
Installing The Controller
Mixing Devices on a Channel
There are numerous types of SCSI devices on the market, and it
may be tempting to mix state-of-the-art devices with others that
may be available. While most combinations will work,
performance will be degraded. Adaptec Ultra320 RAID controllers
are meant to be used to construct arrays using Ultra320 drives and
Ultra320 cables. Mixing any other type of device or cable with
Ultra320 devices may reduce the performance on that channel.
The Adaptec SCSI RAID controllers may be used in LVD mode or
SE mode. To operate at their maximum designed rate, LVD devices
must be connected only with LVD devices on a channel. The cable
used with LVD devices must supply the termination, since LVD
devices do not provide termination. LVD devices will
automatically connect as SE if any SE only device is connected to
that channel.
Caution:
If you have older SCSI-2 devices with a High Voltage
Differential (HVD) interface,
DO NOT USE THEM
with the
Adaptec SCSI RAID controller. Doing so will damage the
controller.
Use of Ultra 2 devices will reduce the performance dramatically!
Other LVD devices attached typically won’t impact the
performance of Ultra320 devices on the same channel, although the
maximum transfer rate of each LVD device will be limited to that
device’s native design speed.
If SCSI devices other than LVD interfaced hard disk drives (SE)
have to be attached to your system, they are best connected either
to a separate SCSI controller, or a channel of the RAID controller
not used by any arrays. This is due to the SE devices limiting the
transfer rate of all devices attached to that channel. SE
specifications allow for maximum connecting cable lengths of
either 1.5 m or 3 m, depending on transfer speed. This alone could
make the addition of an SE device to a working system not
function if the system was operating in LVD mode and using
longer cable lengths as allowed by later versions of SCSI.
!