Integrated HP NetRAID Controller Config. Guide

Glossary
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SAF-TE: SCSI Access Fault-Tolerant Enclosure; a processor that manages a hot-
swap mass storage cage or enclosure.
SCSI Channel: The integrated HP NetRAID controller controls the disk drives
via SCSI-2 buses called "channels" over which the system transfers data in Fast-
and-Wide, Ultra SCSI, or Ultra2 SCSI mode.
SCSI Disk Status: A SCSI disk module (physical drive) can be in one of five
states:
• Ready: a powered-on and operational disk that has not been configured.
• Online: a powered-on and operational disk that has been configured.
• Hot Spare: a powered-on, stand-by disk ready for use should a disk fail.
• Failed: errors on the disk have caused it to fail, or you have used an
HP NetRAID utility to take the drive offline.
• Rebuilding: a disk in the process of having data restored from one or
more critical logical drives.
SCSI ID: Each SCSI device on a SCSI bus must have a different SCSI address
number (Target) from 0 to 15, but not 7, which is reserved for the SCSI
controller. A SCSI ID is also be reserved for the SAF-TE processor, if one is
present on the mass storage enclosure.
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 width. You
may specify a stripe size for each logical drive. A 128-KB stripe requires 8 MB of
memory.
Stripe Width: The number of disk modules across which the data is striped.
Equivalent to the number of disks in the array.
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 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.