Tekram Technology DC-820B - Manual (Page 25)

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EISA Fast SCSI Caching Adapter
Mirrored to SCSI ID: NO/1-7. This disk mirroring function is implemented
by the DC-820B’s firmware and works for all operating systems. This
option needs two and only two drives and is selected from the slave drive’s
point of view. The SCSI ID number you choose stands for the master drive
that you want to mirror to. The NO option may stand for two meanings:
either this drive (master) mirrors to another drive or no mirroring operation is
on this drive at all. So, from the example shown on the setup screen, we can
tell that the fixed drive with SCSI ID 1 (slave) is mirrored to another fixed
drive with SCSI 0 (master). The MO with SCSI ID 2 has NO as its option
and is not involved in any mirroring activity.
When the mirror function is enabled, the mirror-pair related to this operation
would be seen as one. That means a WRITE operation would be performed
on both the master and slave drives. On the other hand, a read operation
would only access the data from the master drive and not the slave. Since a
duplicate copy of the master drive would reside on the slave drive, data
security is ensured in case one of the pair is damaged. One condition of this
option is that the slave drive must have at least the same storage capacity as
the master drive. Besides setting this option properly, you still have to run a
utility program (TOOLBME.EXE) to set up the mirroring initialization.
Refer to the next section for more details about TOOLBME.EXE.
BIOS INT 13H device: HD/HDRM/No. HD (default) option is for fixed
disk drives controlled by BIOS INT 13H and will be ignored if no device is
installed. HDRM option is for fixed disk and removable disk drives con-
trolled by BIOS INT 13H. The No option is for drives controlled by the DC-
820B’s device driver instead of INT 13H. Note that removable disk drives
with the HDRM option selected can only function as fixed disks and are not
allowed to change media. Also, if you set the option as HD for a removable
media device, it can only be recognized by adding a device driver instead of
being controlled through BIOS INT 13H.
MAX Sync Xfer rate: 10.0 - 2.00 MB/sec. DC-820B supports the 10.00
MB/sec as its highest data transfer rate to work with SCSI devices comply-
ing with Fast SCSI protocol. The DC-820B will negotiate an optimum speed
depending on the transfer rate of each device under your chosen option.