Adaptec 2074700-R User Guide - Page 167
Domain Validation
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ICP RAID Navigator Synchronous Transfer and Synchronous Transfer Rate Different from the older asynchronous transfer mode, synchronous transfer offers higher transfer rates on the SCSI bus. The maximum synchronous data transfer rate depends on the width of the SCSI bus (8 bit narrow SCSI, 16 bit wide SCSI) and the frequency of the signals on the SCSI bus (10 MHz for Fast SCSI, 20 MHz for Ultra SCSI and 40 MHz for Ultra2 SCSI and Ultra160/320 SCSI). The maximum data transfer rates are shown in Table 11-17. Table 11-17. Data Transfer Rates Fast SCSI Ultra SCSI Ultra2 SCSI Ultra160 Ultra320 † (LVD SCSI (low voltage differential) only) Narrow SCSI (8Bit) 10 MB/s 20 MB/s - Wide SCSI (16Bit) 20 MB/s 40 MB/s 80 MB/s † 160 MB/s † 320 MB/s † Note: The maximum synchronous data transfer rate between a SCSI device and the ICP RAID controller can be limited. This limitation may become necessary if a particular SCSI cabling does not allow the maximum rate the controller and the drive could achieve. Adjust the synchronous transfer rate in the SCSI parameters / Initialize menu. Note: To select a transfer rate above 10 MB/s the protocol must be set to SCSI-III. Higher frequencies (single ended SCSI) require better cabling, shorter cables and a professional termination of the SCSI bus. Domain Validation Domain Validation is a cyclical check of the correct data transfer at a given rate for ICP RAID controllers with Ultra160 SCSI channels. Normally this parameter is Off. Disconnect This SCSI feature enables a SCSI device to disconnect from the SCSI bus. By releasing the SCSI bus while the device doesn't need it, the bus becomes free for other devices to transfer or receive data. An example of a disconnect situation is a hard disk that needs time to read data from its media after receiving a read command. It may then disconnect from the SCSI bus so that other devices can transfer data. Later on it reconnects when it is able to deliver the data instantly. You can change the disconnect setting for a hard disk in the SCSI parameters / Initialize menu. Software Installation and User's Guide 167