Glossary 5
Rotated XOR Redundancy
This term (also known as “parity”) refers to a method of providing complete data
redundancy while requiring only a fraction of the storage capacity for redundancy. In a
system configured under RAID 3 and 5, all data and parity blocks are divided between the
drives in such a way that if any single drive is removed (or fails), the data on it can be
reconstructed using the data on the remaining drives. (XOR refers to the Boolean
“Exclusive-OR” operator.)
S
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.
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