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Altos RAIDWatch User Guide
Parity . Parity checking is used to detect errors in binary-coded data. The fact that all numbers have
parity is commonly used in data communications to ensure the validity of data. This is called parity
checking.
Primary Agent . The Altos RAIDWatch module which manages secondary agents and supports both
NPC and Altos RAIDWatch Manager.
RAID
Disks"). The use of two or more disk drives instead of one disk, which provides better disk
performance, error recovery, and fault tolerance, and includes interleaved storage techniques and
mirroring of important data. See Appendix D.
Altos RAIDWatch Manager . The GUI RAID interface part of Altos RAIDWatch.
SAN (Storage Area Network) . is a high-speed subnetwork of shared storage devices. A storage
device is a machine that contains nothing but a disk or disks for storing data. A SAN's architecture
works in a way that makes all storage devices available to all servers on a LAN or WAN. Because
stored data does not reside directly on the network's servers, server power is utilized for
applications rather than for data passing.
Secondary Agent . The Altos RAIDWatch module which manages and monitors a RAID controller
and receives Altos RAIDWatch Manager commands via the primary agent.
S.E.S. SCSI Enclosure Services is a protocol that is used to manage and sense the state of the power
supplies, cooling devices, temperature sensors, individual drives, and other non-SCSI elements
installed in a fibre channel JBOD enclosure.
S.M.A.R.T.(Self-Monitoring, Analysis and Reporting Technology). an open standard for developing
disk drives and software systems that automatically monitor a disk drive's health and report
potential problems. Ideally, this should allow users to take proactive actions to prevent impending
disk crashes.
Spare (Local / Global) . A drive designation used in RAID systems for drives that are not used but are
instead "hot-ready" and used to automatically replace a failed drive. RAIDs generally support two
types of spare, Local and Global. Local spares only replace drives that fail in the same logical drive.
Global spares replace any drive in the RAID that fails.
Stripe . A contiguous region of disk space. Stripes may be as small as one sector or may be composed
of many contiguous sectors.
Striping Also called RAID-0. A method of distributing data evenly across all drives in an array by
concatenating interleaved stripes from each drive.
Stripe Size (A.k.a., "chunk size.") . The smallest block of data read from or written to a physical
drive. Modern hardware implementations let users to tune this block to the typical access patterns
of the most common system applications.
Stripe Width . The number of physical drives used for a stripe. As a rule, the wider the stripe, the
better the performance.
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Redundant Arrays of Independent Disks (Originally "Redundant Arrays of Inexpensive
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