User guide

LSI Corporation
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LSI Nytro MegaRAID Application Acceleration Card User Guide
August 2012
Glossary
Glossary
B
BIOS Acronym for Basic Input/Output System. Software that provides basic read/write capability. Usually kept as
firmware (ROM-based). The system BIOS on the motherboard of a computer boots and controls the system.
The BIOS on your host adapter acts as an extension of the system BIOS.
C
Cache Fast memory that holds recently accessed data. Use of cache memory speeds subsequent access to the same
data. When data is read from or written to main memory, a copy is also saved in cache memory with the
associated main memory address. The cache memory software monitors the addresses of subsequent reads
to see if the required data is already stored in cache memory. If it is already in cache memory (a cache hit), it
is read from cache memory immediately and the main memory read is aborted (or not started). If the data is
not cached (a cache miss), it is fetched from main memory and saved in cache memory.
Caching The process of using a high speed memory buffer to speed up a computer system’s overall read/write
performance. The cache can be accessed at a higher speed than a drive subsystem. To improve read
performance, the cache usually contains the most recently accessed data, as well as data from adjacent drive
sectors. To improve write performance, the cache can temporarily store data in accordance with its write
back policies.
D
device driver A program that allows a microprocessor (through the operating system) to direct the operation of a
peripheral device.
drive group A group of physical drives that combines the storage space on the drives into a single segment of storage
space. A hot spare drive does not actively participate in a drive group.
E
external SAS
device
A SAS device installed outside the computer cabinet. These devices are connected using specific types of
shielded cables.
F
Flash Nytro Flash module that is 100x to 1000x faster than hard drives yet provides non-volatility. Flash memory
does not have the mechanical limitations and latencies of hard drives, so a Nytro Flash module is attractive
when considering speed, noise, power consumption, and reliability.
Fusion-MPT
architecture
An acronym for Fusion-Message Passing Technology architecture. Fusion-MPT consists of several main
elements: Fusion-MPT firmware, the Fibre Channel and SCSI hardware, and the operating system level drivers
that support these architectures. Fusion-MPT architecture offers a single binary, operating system driver that
supports both Fibre Channel and SCSI devices.
H
HDD Hard disk drive
host The computer system in which a RAID controller is installed. It uses the RAID controller to transfer
information to and from devices attached to the SCSI bus.
internal SAS
device
A SAS device installed inside the computer cabinet. These devices are connected by using a shielded cable.
I
Internal Drive
Bay
A bay internal the case and usually used for hard disk drives that do not require any access by the user.