Installation guide

Manual No. 775020 G-1
Glossary
Cache
Controller memory used to speed up data transfer to and from a disk.
Cache Flush
Refers to an operation where all unwritten blocks in a Write-Back Cache are
written to the target disk. This operation is necessary before powering down
the system.
Cache Line Size
The Cache Line Size function is set in conjunction with stripe size and
represents the size of the data “chunk” that will be read or written at one
time.
Channel
Refers to one SCSI bus on a disk array controller. Each disk array controller
provides at least one channel.
Consistency Check
Refers to a process where the integrity of redundant data is verified. For
example, a consistency check of a mirrored drive will make sure that the data
on both drives of the mirrored pair is exactly the same.
Disk Failure Detection
The controller automatically detects SCSI disk failures. A monitoring
process running on the controller checks, among other things, elapsed time
on all commands issued to disks. A time-out causes the disk to be “reset”
and the command to be retried. If the command times out again, the disk
could be “killed” (taken “offline”) by the controller (its state changed to
“dead”). DAC960 controllers also monitor SCSI bus parity errors and other
potential problems. Any disk with too many errors will also be ‘killed’.