Glossary
105
F
AULT
T
OLERANCE
—Fault tolerance is the capability of the disk subsystem to
undergo a single drive failure for the physical disks in a virtual disk without
compromising data integrity and processing capability. The PERC S100 controller and
PERC S300 controller provide this support through redundant virtual disks in RAID
levels 1, 5 and 10. Fault tolerance is often associated with system availability because it
allows the system to be available during drive failures. In case a disk fails, the PERC
S100 controller and
PERC S300 controller support hot spare disks and the auto-rebuild feature.
F
IRMWARE
—Software stored in read-only memory (ROM) or Programmable ROM
(PROM). Firmware is often responsible for the behavior of a system when it is first
turned on. A typical example would be a monitor program in a system that loads the
full operating system from disk or from a network and then passes control to the
operating system.
F
ORMAT
—The process of writing a specific value to all data fields on a physical disk,
to map out unreadable or bad sectors. Because most physical disks are formatted when
manufactured, formatting is usually done only if a physical disk generates many media
errors.
GB — Acronym for gigabyte(s). A gigabyte equals 1,024 megabytes or 1,073,741,824
bytes (2^30 bytes).
GPT (GUID P
ARTITION
T
ABLE
)—A standard for the layout of the partition table
on a physical hard disk.
G
LOBALLY
U
NIQUE
I
DENTIFIER
(GUID) — A unique reference-number identifier
used in software applications.
HBA (H
OST
B
US
A
DAPTOR
)—An adaptor card that includes the I/O logic, software
and processing to manage the transfer of information between the host system and
devices connected to it.
H
OST
S
YSTEM
—Any system on which the RAID controller is installed. Mainframes,
workstations, and personal systems can all be considered host systems.
H
OT
S
PARE
—An idle, powered on, stand-by physical disk ready for immediate use
in case of disk failure. It does not contain any user data. A hot spare can be dedicated
to a single redundant virtual disk or it can be part of the global hot-spare pool for all
virtual disks controlled by the controller. When a disk fails, the PERC S100 controller
or PERC S300 controller automatically replaces and rebuilds the data from the failed
physical disk to the hot spare. Data can be rebuilt only from virtual disks with
redundancy (RAID levels 1, 5, or 10; not RAID 0), and the hot spare must have
sufficient capacity. If the hot spare is designated as having enclosure affinity, it
attempts to rebuild any failed disks on the backplane within which it resides before
rebuilding any other on other backplanes.
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