Intel 12Gb/s, Руководство пользователя

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12Gb/s Intel® RAID Controllers User Guide 35
RAID levels A set of techniques applied to drive groups to deliver higher data availability,
performance characteristics, or both to host environments. Each virtual drive must
have a RAID level assigned to it.
S
SAS Acronym for Serial Attached SCSI. A serial, point-to-point, enterprise-level device
interface that leverages the proven SCSI protocol set. The SAS interface provides
improved performance, simplified cabling, smaller connections, lower pin count, and
lower power requirements when compared to parallel SCSI. SAS controllers leverage
a common electrical and physical connection interface that is compatible with Serial
ATA.
The SAS controllers support the ANSI Serial Attached SCSI Standard, Version 2.0 . In
addition, the controller supports the Serial ATA III (SATA III) protocol defined by the
Serial ATA Specification, Version 3.0 . Supporting both the SAS interface and the
SATA III interface, the SAS controller is a versatile controller that provides the
backbone of both server and high-end workstation environments. Each port on the
SAS RAID controller supports SAS devices, SATA devices, or both.
SAS device Any device that conforms to the SAS standard and is attached to the SAS bus by a
SAS cable. This includes SAS RAID controllers (host adapters) and SAS peripherals.
SATA Acronym for Serial Advanced Technology Attachment. A physical storage interface
standard, SATA is a serial link that provides point-to-point connections between
devices. The thinner serial cables allow for better airflow within the system and permit
smaller chassis designs.
SMP Acronym for Serial Management Protocol. SMP communicates topology management
information directly with an attached SAS expander device. Each PHY on the
controller can function as an SMP initiator.
SSP Acronym for Serial SCSI Protocol. SSP enables communication with other SAS
devices. Each PHY on the SAS controller can function as an SSP initiator or an SSP
target.
STP Acronym for Serial Tunneling Protocol. STP enables communication with a SATA
device through an attached expander. Each PHY on the SAS controller can function
as an STP initiator.
strip The portion of a stripe that resides on a single drive.
stripe size The total drive space consumed by a stripe not including a parity drive. For example, if
a stripe contains 64 KB of drive space and has 16 KB of data residing on each drive,
the stripe size is 64 KB and the strip size is 16 KB.
A larger stripe size produces improved read performance, especially if most of the
reads are sequential. For mostly random reads, select a smaller stripe size.
striping Drive striping writes data across two or more drives. Each stripe spans two or more
drives but consumes only a portion of each drive. Each drive, therefore, may have
several stripes. The amount of space consumed by a stripe is the same on each drive
that is included in the stripe. The portion of a stripe that resides on a single drive is a
strip, also known as a stripe element. Striping by itself does not provide data
redundancy; striping in combination with parity provides data redundancy.
strip size The drive space consumed by a strip. For example, if a stripe contains 64 KB of drive
space and has 16 KB of data residing on each drive, the stripe size is 64 KB and the
strip size is 16 KB. The stripe depth is four (four drives in the stripe). You can specify
strip sizes of 8 KB, 16 KB, 32 KB, 64 KB, 128 KB, 256 KB, 512 KB, or 1 MB.