User guide

1-6 Compaq Smart Array 431 Controller User Guide
LVD and SE Signaling
Both Wide Ultra3 and Wide Ultra2 SCSI devices use Low Voltage
Differential (LVD) signaling on the SCSI bus. LVD allows devices to run at
higher speeds and at longer distances. Wide-Ultra SCSI devices use Single
Ended (SE) signaling on the SCSI bus, which is an older technology.
LVD and SE signaling are not supported concurrently on the same SCSI bus.
Therefore, if SCSI devices that supports LVD signaling are placed on the same
SCSI bus as SCSI devices that support SE signaling, then the LVD SCSI
devices will revert to SE signaling to maintain compatibility. Since the Wide
Ultra2 and Wide Ultra3 standards require LVD signaling, this means that those
SCSI devices will operate at Wide-Ultra speeds since that is the only standard
support by Compaq with SE signaling.
If all of the SCSI devices on the SCSI bus use LVD signaling, they will be
compatible with each other. Wide Ultra2 and Wide Ultra3 SCSI devices can
coexist and run at their respective maximum speeds per the appropriate SCSI
standard.
Maximizing Performance
Compaq recommends using only Wide Ultra2 and Wide Ultra3 SCSI devices
on the same SCSI bus for maximum performance. Combining LVD and SE
SCSI devices on the same SCSI bus will decrease the overall performance to
Wide-Ultra speeds.
Array Configuration Utilities
Options Rom Configuration for Arrays (ORCA)
The Options Rom Configuration for Arrays utility will allow you to configure
your array controller. ORCA is designed for those with minimal configuration
requirements, and a moderate knowledge level of RAID technology. This
utility:
■ Can be started while the server is booting
■ Does not require diskettes or CD-ROM drives to run
■ Can only configure a single logical drive
■ Has minimal control over the physical configuration
■ With certain requirements, can be executed at a later time
■ Supports English language only