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When a drive fails, MegaRAID Storage Manager software automatically uses a hot spare to
replace it and then rebuilds the data from the failed drive to the hot spare. Hot spares can be used
in RAID 1, 5, 6, 10, 50, and 60 storage configurations.
initialization – The process of writing zeros to the data fields of a virtual drive and, in fault-
tolerant RAID levels, generating the corresponding parity to put the virtual drive in a Ready state.
Initialization erases all previous data on the drives. Drive groups will work without initializing, but
they can fail a consistency check because the parity fields have not been generated.
IO policy – A virtual drive property indicating whether Cached I/O or Direct I/O is being used. In
Cached I/O mode, all reads are buffered in cache memory. In Direct I/O mode, reads are not
buffered in cache memory. Data is transferred to cache and the host concurrently. If the same
data block is read again, it comes from cache memory. (The IO Policy applies to reads on a
specific virtual drive. It does not affect the read ahead cache.)
LKM – Local Key Management
load-balancing – A method of spreading work between two or more computers, network links,
CPUs, drives, or other resources. Load balancing is used to maximize resource use, throughput,
or response time.
media error count – A drive property indicating the number of errors that have been detected on
the drive media.
migration – The process of moving virtual drives and hot spare drives from one controller to
another by disconnecting the drives from one controller and attaching them to another one. The
firmware on the new controller will detect and retain the virtual drive information on the drives.
mirroring – The process of providing complete data redundancy with two drives by maintaining
an exact copy of one drive's data on the second drive. If one drive fails, the contents of the other
drive can be used to maintain the integrity of the system and to rebuild the failed drive.
multipathing – The firmware provides support for detecting and using multiple paths from the
RAID controllers to the SAS devices that are in enclosures. Devices connected to enclosures have
multiple paths to them. With redundant paths to the same port of a device, if one path fails,
another path can be used to communicate between the controller and the device. Using multiple
paths with load balancing, instead of a single path, can increase reliability through redundancy.
name – A virtual drive property indicating the user-assigned name of the virtual drive.
non-redundant configuration – A RAID 0 virtual drive with data striped across two or more
drives but without drive mirroring or parity. This provides for high data throughput but offers no
protection in case of a drive failure.
NVRAM – Acronym for non-volatile random access memory. A storage system that does not lose
the data stored on it when power is removed. NVRAM is used to store firmware and configuration
data on the RAID controller.
NVRAM present – A controller property indicating whether an NVRAM is present on the
controller.
NVRAM size – A controller property indicating the capacity of the controller's NVRAM.
Glossary
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DB09-000202-05 37857-02
Rev. F - May 2011
Copyright © 2011 by LSI Corporation. All rights reserved.
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