Adaptec 2200S - SCSI RAID Controller Guide d'installation télécharger pdf (Page 22)

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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.

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Adaptec 2200S - SCSI RAID Controller Guide d'installation Page 22