Avago Technologies Cache Protection for RAID Controller Cards User Manual
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LSI Corporation
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12Gb/s MegaRAID SAS RAID Controllers User Guide
April 2014
Glossary
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.