HP NetRAID 1Si Controller User Manual
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Glossary
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SCSI ID: Each SCSI device on an HP NetRAID SCSI bus must have a different
SCSI address number (Target ID, or TID) from 0 to 15, but not 7, which is
reserved for the SCSI controller. Drives IDs are determined by the slot positions
or are set by switches. Consult your HP NetServer documentation and chassis
labels for slot position IDs or correct switch settings.
SNMP: (Simple Network Management Protocol) The Internet standard protocol
developed to manage nodes on an Internet Protocol (IP) network.
Spare: A hard drive available to back up the data of other drives.
Striping: Segmentation of logically sequential data, such as a single file, so that
segments can be written to multiple physical devices in a round-robin fashion.
This technique is useful if the processor is capable of reading or writing data faster
than a single disk can supply or accept it. While data is being transferred from the
first disk, the second disk can locate the next segment. Data striping is used in
some modern databases and in certain RAID devices. In an inconsistent stripe,
firmware always updates the parity stripe to restore consistency.
Stripe Size: The amount of data contiguously written to each disk. Also called
"stripe depth." You can specify stripe sizes of 2 KB, 4 KB, 8 KB, 16 KB, 32 KB,
64 KB, and 128 KB, for each logical drive. For best performance, choose a stripe
size equal to or smaller than the block size used by your host operating system. A
larger stripe depth produces higher read performance, especially if most of the
reads are sequential. For mostly random reads, select a smaller stripe size. You
can specify a stripe size for each logical drive.
Stripe Width: The number of disk modules across which the data is striped. The
stripe width is equivalent to the number of disks in the array.
Terminator: A resistor or other mechanism connected to a signal wire in a bus or
network for the purpose of impedance matching to prevent reflections. SCSI
chains require terminators.
Ultra2 SCSI: Drives that operate at SCSI bus data rates of up to 80 MB per
second--double the rate of Ultra/Wide SCSI. Ultra2 drives are sometimes referred
to as LVD (low voltage differential) drives.
Ultra SCSI: An extension of SCSI-2, proposed by a group of manufacturers,
which doubles the transfer speed of Fast-SCSI to give 20 MB/s on an 8-bit
connection and 40 MB/s on a 16-bit connection.
Wide SCSI: A variant on the SCSI-2 interface. It uses a 16-bit bus, double the
width of the original SCSI-1, and therefore cannot be connected to a SCSI-1 bus.
It supports transfer rates up to 20 MBs, like Fast SCSI.