Glossary
DataDirect Networks EF2800 FC RAID Storage System User Guide (V 1.0)
339
Storage Man-
ager mod-
ule
The controller module which includes an FC-AL 2Gb/s LRC I/O module
with integral EF2800 RAID controller.
target A target is a device (peripheral) that responds to an operation
requested by an initiator (host system). Although peripherals are
generally targets, a peripheral may be required to act temporarily as an
initiator for some commands (for example, SCSI EXTENDED COPY
command).
terminator
block/ter-
mination
A terminator block (or termination) refers to the electrical connection
at each end of a SCSI bus. The terminator block is composed of a set of
resistors, or possibly other components. The function of a terminator
block is to provide a pull-up for open collector drivers on the bus, and
also impedance matching to prevent signal reflections at the ends of the
cable. SCSI buses require that a terminator be placed on the 68-pin high-
density SCSI connector on the last SCSI peripheral. Data errors may
occur in a SCSI bus that is not terminated.
topology A network topology refers to the physical layout of nodes on a network.
Topologies range from local network topologies to WAN topologies. FC
topologies include point-to-point, FC-AL, and fabric.
trap In the context of SNMP, a trap is an unsolicited message sent by an
agent to a management station. The purpose is to notify the
management station of some unusual event.
unkill In Active-Active mode, when a surviving controller removes the reset
from the other controller, it unkills it. The other controller will reboot
and attempt to come online.
write-back
cache
Memory on the controller that stores data changes until they are
written to the disk drives. In most applications, using the controller’s
write-back cache improves performance and ensures data integrity.
Disk drives also have write-back cache, which should be disabled for
most applications. Any disk drives with write-back cache enabled
should be connected to an Uninterruptible power supply (UPS) in case
of a power failure. If the drives are not on a UPS and power is lost
during disk writes, the array will lose any data in the disk’s write-back
cache.
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