Glossary
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SAF-TE Is the acronym for SCSI Accessed Fault-Tolerant
Enclosures. It is a monitoring and communication
specification developed by Conner (nStor) and Intel for
sending and receiving server and storage system status
information via the SCSI bus.
Session Refers to the period of time between any two consecutive
system shutdowns. System shutdown may be either a
power off/on, or a hardware reset.
SCSI Drive A disk drive equipped with a small computer system
interface (SCSI). Each disk drive will be assigned a SCSI
address (or SCSI ID), which is a number from 0 to 15. The
SCSI address uniquely identifies the drive on the SCSI bus
or channel.
Spanning Disk spanning allows multiple disk drives to function like
one big drive. Spanning overcomes lack of disk space and
simplifies storage management by combining existing
resources or adding relatively inexpensive resources.
Striping Disk striping writes data across multiple disks rather than
on one disk. disk striping involves partitioning each drive
storage space into stripes that can vary in size from one
sector (1 KB) to several megabytes.
Stripe Order The order in which SCSI Drives appear within a Physical
Pack. This order must be maintained, and is critical to the
controller’s ability to “Rebuild” failed drives.
Stripe Width Refers to the number of kilobytes per stripe block.
Target ID A target ID is the SCSI ID of a device attached to the disk
array controller. Each SCSI channel can have up to
sixteen SCSI devices (target ID from 0 to 15) attached to
it.
Write-Through Cache Refers to a cache writing strategy whereby data is written
to the SCSI Drive before a completion status is returned to
the host operating system. This caching strategy is
considered more “secure,” since a power failure will be
less likely to cause loss of data. However, a Write-Through
cache results in a slightly lower performance, in most
environments.
Write-Back Cache Refers to a caching strategy whereby write operations
result in a completion signal being sent to the host
operating system as soon as the cache (not the disk drive)
receives the data to be written. The target SCSI Drive will
receive that data at a more appropriate time, in order to
increase controller performance.