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offline – A drive is offline when it is part of a virtual drive but its data is not accessible to the
virtual drive.
patrol read – A process that checks the drives in a storage configuration for drive errors that
could lead to drive failure and lost data. The patrol read operation can find and sometimes fix any
potential problem with drives prior to host access. This enhances overall system performance
because error recovery during a normal I/O operation may not be necessary.
patrol read rate – The user-defined rate at which patrol read operations are run on a computer
system.
product info – A drive property indicating the vendor-assigned model number of the drive.
product name – A controller property indicating the manufacturing name of the controller.
RAID – A group of multiple, independent drives that provide high performance by increasing the
number of drives used for saving and accessing data.
A RAID drive group improves input/output (I/O) performance and data availability. The group of
drives appears to the host system as a single storage unit or as multiple virtual drives. Data
throughput improves because several drives can be accessed simultaneously. RAID
configurations also improve data storage availability and fault tolerance. Redundant RAID levels
(RAID levels 1, 5, 6, 10, 50, and 60) provide data protection.
RAID 0 – Uses data striping on one or more drives to provide high data throughput, especially for
large files in an environment that requires no data redundancy.
RAID 00 – Uses data striping on two or more drives in a spanned drive group to provide high data
throughput, especially for large files in an environment that requires no data redundancy.
RAID 1 – Uses data mirroring on pairs of drives so that data written to one drive is simultaneously
written to the other drive. RAID 1 works well for small databases or other small applications that
require complete data redundancy.
RAID 5 – Uses data striping and parity data across three or more drives (distributed parity) to
provide high data throughput and data redundancy, especially for applications that require random
access.
RAID 6 – Uses data striping and parity data across three or more drives (distributed parity) to
provide high data throughput and data redundancy, especially for applications that require random
access. RAID 6 can survive the failure of two drives.
RAID 10 – A combination of RAID 0 and RAID 1 that uses data striping across two mirrored drive
groups. It provides high data throughput and complete data redundancy.
RAID 50 – A combination of RAID 0 and RAID 5 that uses data striping across two drive groups
with parity data. It provides high data throughput and complete data redundancy.
RAID 60 – A combination of RAID 0 and RAID 6 that uses data striping across two drive groups
with parity data. It provides high data throughput and complete data redundancy. RAID 60 can
survive the failure of two drives in each RAID set in the spanned drive group.
RAID level – A virtual drive property indicating the RAID level of the virtual drive.
MegaRAID SAS RAID controllers support RAID levels 0, 1, 5, 6, 00, 10, 50, and 60.
Page 176
Glossary
DB09-000202-05 37857-02
Rev. F - May 2011
Copyright © 2011 by LSI Corporation. All rights reserved.
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