ICP GDT RS Series, Руководство пользователя

Страница: 135 / 186

135
J.4.4.1 Menu Advanced Setup: Configure Phys. Devs., SCSI Parameter /Initialize
This option can destroy all data on the hard disk.
If a hard disk is not
yet initialized, you
have to initialize it
first. ICPCON cop-
ies ICP specific
configuration
blocks on the hard
disk, a primary
block and a mir-
rored secondary
block. The possible
settings are differ-
ent if you select a
SCSI hard disk or a
Fibre Channel hard
disk. With a FCAL
hard disk there are only a few settings which are relevant. You should always check that
they are all "Enabled" or "On". If the hard disk you have selected is an Ultra 160 device and
the ICP Controller has Ultra 160 SCSI channels, F4 “Advanced Configuration“, allows you to
configure the so-called “Domain Validation“ (a cyclical check of the correct data transfer at
a given rate). Normally this parameter is On.
The various settings have the following meanings:
Sync. Transfer: Enabled
The SCSI-bus knows two methods of data transfer: asynchronous and synchronous transfer.
Each SCSI device must be able to perform the first type of transfer, the second one is op-
tional. The advantage of the synchronous transfer consists in a higher data transfer rate,
since the signal transfer times on the possibly long SCSI-cable have no influence on the
transfer rate anymore. Two SCSI-bus participants which want to exchange data between
each other have to check if and how (i.e., with which parameters) a synchronous data
transfer between them is possible. Therefore, the mere setting does not automatically en-
able synchronous data transfer; this mode is only effective if both devices support it and
after they have checked their capability of communicating with each other in this mode.
Sync. Transfer Rate
This is the synchronous data transfer rate in MB/s. Ultra 160 SCSI allows up to 160 MB/s.
If a given SCSI-cable does not allow a certain transfer rate, it can be reduced to a value that
allows a trouble-free data transfer. The reason for such a restriction is not necessarily a
"bad" SCSI-cable. Lowering the transfer rate may also become necessary when you set up a
special configuration which does not allow full speed.
Disconnect: Enabled
The concept of the SCSI-bus allows several participants. It is particularly important to guar-
antee a high degree of action overlapping on the SCSI-bus. This high degree of overlapping
becomes possible when a SCSI device has an enabled “Disconnect”.
Disk Read Cache / Disk Write Cache / Tagged Queues
Out of performance reasons, the read ahead and write cache of the hard disk should be al-
ways On. Tagged Queues is a SCSI feature which allows the drive to execute more than one
command at a time, if available, it should also be On.