Adaptec 29320LPE User Guide - Page 17

Using SCSI Devices, Using SCSI Disk Drives, Using Ultra320 and Ultra160 Disk Drives - performance

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Chapter 4: Understanding SCSI ● 17 Since the method for terminating a SCSI device can vary widely, refer to the device's documentation for instructions on how to enable or disable termination. Here are some general guidelines for termination: ● Internal Ultra320, Ultra160, and Ultra2 SCSI LVD devices come from the factory with termination disabled and cannot be changed. Proper termination for these internal devices is provided by the built-in terminator at the end of the 68-pin internal LVD SCSI cable. ● Termination on SE internal SCSI devices is usually controlled by manually setting a jumper or a switch on the device, or by physically removing or installing one or more resistor modules on the device. ● Termination on most external SCSI devices is controlled by installing or removing a SCSI terminator. However, termination on some external SCSI devices is enabled or disabled by setting a switch on the back of the SCSI device. ● By default, termination on an Adaptec SCSI Card itself is set to Automatic (the preferred method). We recommend that you do not change this default setting. This automatic setting is just for the Adaptec SCSI Card itself; the card cannot change the termination setting on a device. ● Internal and external Ultra320, Ultra 160, and Ultra2 SCSI LVD SCSI buses must be terminated with an LVD terminator. This is sometimes referred to as an LVD terminator or a Multi-Mode terminator. Using SCSI Devices Using SCSI Disk Drives If you connect a SCSI disk drive to an Adaptec SCSI card that was previously connected to a different SCSI card, it is recommended that you low-level format the drive before you can use it. Back up the data on the drive before moving the drive to the new SCSI card and before you format the drive. (SeeUsing SCSI Disk Utilities on page 43 for information on using the SCSISelect format utility.) ! Caution: A low-level format destroys all data on the drive. Be sure to back up the data before performing a low-level format. Every SCSI disk drive must be physically low-level formatted, partitioned, and logically formatted before it can be used to store data. For instructions on how to partition and format your SCSI disk drives, refer to your operating system documentation. Using Ultra320 and Ultra160 Disk Drives Adaptec recommends that you connect your LVD (Ultra 320, Ultra160, and Ultra2) SCSI devices to one SCSI Channel (bus) and your non-LVD SCSI devices (if any) to a separate SCSI Channel (bus). This allows the LVD SCSI devices to run at their maximum performance levels of 320 MB/sec, 160 MB/sec. or 80 MB/sec. If you combine LVD and non-LVD SCSI devices on the same SCSI channel, the data transfer rate of the LVD SCSI devices will drop down to nonLVD SCSI performance levels of up to 40 MB/sec. Internal LVD SCSI devices come from the factory with termination disabled and cannot be changed. Proper termination is provided by the terminator at the end of the internal LVD SCSI cable.

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Chapter 4: Understanding SCSI
●
17
Since the method for terminating a SCSI device can vary widely, refer to the device’s
documentation for instructions on how to enable or disable termination. Here are some
general guidelines for termination:
●
Internal Ultra320, Ultra160, and Ultra2 SCSI LVD devices come from the factory with
termination disabled and cannot be changed. Proper termination for these internal devices
is provided by the built-in terminator at the end of the 68-pin internal LVD SCSI cable.
●
Termination on SE internal SCSI devices is usually controlled by manually setting a jumper
or a switch on the device, or by physically removing or installing one or more resistor
modules on the device.
●
Termination on most external SCSI devices is controlled by installing or removing a SCSI
terminator. However, termination on some external SCSI devices is enabled or disabled by
setting a switch on the back of the SCSI device.
●
By default, termination on an Adaptec SCSI Card itself is set to Automatic (the preferred
method). We recommend that you do not change this default setting. This automatic
setting is just for the Adaptec SCSI Card itself; the card cannot change the termination
setting on a device.
●
Internal and external Ultra320, Ultra 160, and Ultra2 SCSI LVD SCSI buses must be
terminated with an LVD terminator. This is sometimes referred to as an LVD terminator or
a Multi-Mode terminator.
Using SCSI Devices
Using SCSI Disk Drives
If you connect a SCSI disk drive to an Adaptec SCSI card that was previously connected to a
different SCSI card, it is recommended that you low-level format the drive before you can use
it. Back up the data on the drive before moving the drive to the new SCSI card and before you
format the drive. (See
Using SCSI Disk Utilities
on page 43
for information on using the
SCSI
Select
format utility.)
Caution:
A low-level format destroys all data on the drive. Be sure to back up the data before
performing a low-level format.
Every SCSI disk drive must be physically low-level formatted, partitioned, and logically
formatted before it can be used to store data. For instructions on how to partition and format
your SCSI disk drives, refer to your operating system documentation.
Using Ultra320 and Ultra160 Disk Drives
Adaptec recommends that you connect your LVD (Ultra 320, Ultra160, and Ultra2) SCSI
devices to one SCSI Channel (bus) and your non-LVD SCSI devices (if any) to a separate SCSI
Channel (bus). This allows the LVD SCSI devices to run at their maximum performance levels
of 320 MB/sec, 160 MB/sec. or 80 MB/sec. If you combine LVD and non-LVD SCSI devices on
the same SCSI channel, the data transfer rate of the LVD SCSI devices will drop down to non-
LVD SCSI performance levels of up to 40 MB/sec.
Internal LVD SCSI devices come from the factory with termination disabled and cannot be
changed. Proper termination is provided by the terminator at the end of the internal LVD SCSI
cable.
!