HP LH4r Integrated HP NetRaid Controller Configuration Guide - Page 133

and-Wide, Ultra SCSI, or Ultra2 SCSI mode. An integrated HP NetRAID

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Glossary RAID levels 10, 30, and 50 result when logical drives span arrays. Table 2-2 in Chapter 2 describes RAID levels for logical drives that span arrays. • RAID 10 results when a RAID 1 logical drive spans arrays. • RAID 30 results when a RAID 3 logical drive spans arrays. • RAID 50 results when a RAID 5 logical drive spans arrays. Read Policy: The three Read policies for HP NetRAID are: • Read-Ahead: This is a memory caching ability that tells the controller to read sequentially ahead of requested data and cache the further data in memory, anticipating that the further data will be requested. Read-Ahead supplies sequential data faster, but is not as effective when accessing random data. • Normal: This policy does not use the read-ahead memory caching feature. This policy is efficient when most of the data reads are random. • Adaptive: Adaptive policy causes the read-ahead feature to be used if the last two disk accesses were in sequential sectors. Ready State: A condition in which a workable hard drive is neither online nor a hot spare, and therefore is available to add to an array, or to designate as a hot spare. Rebuild: The regeneration of all data from a failed disk in a RAID level 1, 3, 5, 10, 30, or 50 array to a replacement disk. A disk rebuild normally occurs without interruption of application access to data stored on the logical drive. Rebuild Rate: The speed at which the rebuild operation proceeds. Each controller is assigned a rebuild rate, which specifies the percentage of IOP resources to be devoted to rebuild operations. Reconstruct: The act of remaking a logical drive after changing RAID levels. Redundancy: See RAID Levels SCSI Channel: The integrated HP NetRAID controller controls the disk drives via SCSI-2 buses called "channels" over which the system transfers data in Fastand-Wide, Ultra SCSI, or Ultra2 SCSI mode. An integrated HP NetRAID controller can manage one or two SCSI channels. 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. 127

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Glossary
127
RAID levels 10, 30, and 50 result when logical drives span arrays. Table 2-2 in
Chapter 2 describes RAID levels for logical drives that span arrays.
•
RAID 10
results when a RAID 1 logical drive spans arrays.
•
RAID 30
results when a RAID 3 logical drive spans arrays.
•
RAID 50
results when a RAID 5 logical drive spans arrays.
Read Policy:
The three Read policies for HP NetRAID are:
•
Read-Ahead
: This is a memory caching ability that tells the controller to
read sequentially ahead of requested data and cache the further data in
memory, anticipating that the further data will be requested. Read-Ahead
supplies sequential data faster, but is not as effective when accessing
random data.
•
Normal
: This policy does not use the read-ahead memory caching feature.
This policy is efficient when most of the data reads are random.
•
Adaptive
: Adaptive policy causes the read-ahead feature to be used if the
last two disk accesses were in sequential sectors.
Ready State
: A condition in which a workable hard drive is neither online nor a
hot spare, and therefore is available to add to an array, or to designate as a hot
spare.
Rebuild
: The regeneration of all data from a failed disk in a RAID level 1, 3, 5,
10, 30, or 50 array to a replacement disk. A disk rebuild normally occurs without
interruption of application access to data stored on the logical drive.
Rebuild Rate
: The speed at which the rebuild operation proceeds. Each
controller is assigned a rebuild rate, which specifies the percentage of IOP
resources to be devoted to rebuild operations.
Reconstruct
: The act of remaking a logical drive after changing RAID levels.
Redundancy:
See
RAID Levels
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. An integrated HP NetRAID
controller can manage one or two SCSI channels.
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.