Mylex AcceleRAID 170, Installation Manual

Page: 69 / 86

Glossary
Manual No. 775064 G-13
Offline
A Logical Drive is in an “offline” state if no data can be read from it or
written to it. Offline does not apply to physical disk drives. System
commands issued to offline logical drives are returned with an error status;
no operations can be performed on offline logical drives. See also
Logical
Drive States , Online , and Critical .
Online
A Logical Drive is in an “online” state if all of its participating SCSI drives
have power and are operational. See also Logical Drive States , Critical , and
Offline .
Parity
A method of providing complete data redundancy while requiring only a
fraction of the storage capacity of mirroring. The data and parity blocks are
divided between the disk drives in such a way that if any single disk drive is
removed or fails, the data on it can be reconstructed using the data on the
remaining disk drives. The parity data may exist on only one disk drive or be
distributed between all disk drives in a RAID group.
Parity Check
A function used to verify the integrity of data on a system drive. It verifies
that mirror or parity information matches the stored data on the redundant
arrays. If the parity block information is inconsistent with the data blocks,
the controller corrects the inconsistencies. See also
Consistency Check .
PCI
Peripheral Component Interconnect, a standardized architecture that
provides a high-speed data path between peripherals and the CPU. PCI is a
high-performance, backplane interface, expansion slot architecture found on
PCs, Macintoshes, and UNIX workstations. PCI cards are portable across
hardware platforms with the help of various software drivers.
PCI Hot Plug
A feature that allows for the printed circuit board (PCB) to be replaced
without powering down the entire system—an essential feature in newer
PCI-based PCs. Mylex DAC960PG, DAC960PJ, AcceleRAID, and
eXtremeRAID products are all PCI Hot Plug compatible. See also
Hot Plug .