LSI 1600 Manual De Usuario
Glossary
129
Glossary
Array
A grouping or array of disk drives combines the storage space on the disk drives into a single
segment of contiguous storage space. MegaRAID can group disk drives on one or more SCSI
channels into an array. A hot spare drive does not participate in an array.
segment of contiguous storage space. MegaRAID can group disk drives on one or more SCSI
channels into an array. A hot spare drive does not participate in an array.
Array Management Software Software that provides common control and management for a disk array. Array
Management Software most often executes in a disk controller or intelligent host bus adapter, but
can also execute in a host computer. When it executes in a disk controller or adapter, Array
Management Software is often called firmware.
can also execute in a host computer. When it executes in a disk controller or adapter, Array
Management Software is often called firmware.
Array Spanning Array spanning by a logical drive combines storage space in two arrays of disk drives into a single,
contiguous storage space in a logical drive. MegaRAID logical drives can span consecutively
numbered arrays that each consist of the same number of disk drives. Array spanning promotes
RAID levels 1, 3, and 5 to RAID levels 10, 30, and 50, respectively. See also Disk Spanning.
numbered arrays that each consist of the same number of disk drives. Array spanning promotes
RAID levels 1, 3, and 5 to RAID levels 10, 30, and 50, respectively. See also Disk Spanning.
Asynchronous Operations Operations that bear no relationship to each other in time and can overlap. The concept
of asynchronous I/O operations is central to independent access arrays in throughput-intensive
applications.
applications.
Cache I/O
A small amount of fast memory that holds recently accessed data. Caching speeds subsequent
access to the same data. It is most often applied to processor-memory access, but can also be used
to store a copy of data accessible over a network. 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.
access to the same data. It is most often applied to processor-memory access, but can also be used
to store a copy of data accessible over a network. 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.
Channel
An electrical path for the transfer of data and control information between a disk and a disk
controller.
controller.
Consistency Check An examination of the disk system to determine whether all conditions are valid for the
specified configuration (such as parity.)
Cold Swap
A cold swap requires that you turn the power off before replacing a defective hard drive in a disk
subsystem.
subsystem.
Data Transfer Capacity The amount of data per unit time moved through a channel. For disk I/O, bandwidth is
expressed in megabytes per second (MB/s).
Degraded
A drive that has become non-functional or has decreased in performance.
Disk
A non-volatile, randomly addressable, rewritable mass storage device, including both rotating
magnetic and optical disks and solid-state disks, or non-volatile electronic storage elements. It does
not include specialized devices such as write-once-read-many (WORM) optical disks, nor does it
include so-called RAM disks implemented using software to control a dedicated portion of a host
computer volatile random access memory.
magnetic and optical disks and solid-state disks, or non-volatile electronic storage elements. It does
not include specialized devices such as write-once-read-many (WORM) optical disks, nor does it
include so-called RAM disks implemented using software to control a dedicated portion of a host
computer volatile random access memory.
Cont’d