Avago Technologies MegaRAID Fast Path Software - Manual (Page 496)

Page 496 LSI Corporation Confidential | July 2011
MegaRAID SAS Software User Guide Appendix C: Glossary
read policy A controller attribute indicating the current Read Policy mode. In Always Read Ahead
mode, the controller reads sequentially ahead of requested data and stores the
additional data in cache memory, anticipating that the data will be needed soon. This
speeds up reads for sequential data, but there is little improvement when accessing
random data. In No Read Ahead mode (known as Normal mode in WebBIOS), read
ahead capability is disabled.
rebuild The regeneration of all data to a replacement drive in a redundant virtual drive after a
drive failure. A drive rebuild normally occurs without interrupting normal operations
on the affected virtual drive, though some degradation of performance of the drive
subsystem can occur.
rebuild rate The percentage of central processing unit (CPU) resources devoted to rebuilding data
onto a new drive after a drive in a storage configuration has failed.
reclaim virtual drive A method of undoing the configuration of a new virtual drive. If you highlight the
virtual drive in the Configuration Wizard and click Reclaim, the individual drives are
removed from the virtual drive configuration.
reconstruction rate The user-defined rate at which a drive group modification operation is carried out.
redundancy A property of a storage configuration that prevents data from being lost when one
drive fails in the configuration.
redundant configuration A virtual drive that has redundant data on drives in the drive group that can be used to
rebuild a failed drive. The redundant data can be parity data striped across multiple
drives in a drive group, or it can be a complete mirrored copy of the data stored on a
second drive.
A redundant configuration protects the data in case a drive fails in the configuration.
revertible hot spare When you use the Replace Member procedure, after data is copied from a hot spare to
a new drive, the hot spare reverts from a rebuild drive to its original hot spare status.
revision level A drive property that indicates the revision level of the drive’s firmware.
SAS Acronym for Serial Attached SCSI. SAS is a serial, point-to-point, enterprise-level device
interface that leverages the Small Computer System Interface (SCSI) protocol set. The
SAS interface provides improved performance, simplified cabling, smaller connectors,
lower pin count, and lower power requirements when compared to parallel SCSI.
SATA Acronym for Serial Advanced Technology Attachment. A physical storage interface
standard. SATA is a serial link that provides point-to-point connections between
devices. The thinner serial cables allow for better airflow within the system and permit
smaller chassis designs.
SCSI device type A drive property indicating the type of the device, such as drive.
serial no. A controller property indicating the manufacturer-assigned serial number.
strip size The portion of a stripe that resides on a single drive in the drive group.
stripe size A virtual drive property indicating the length of the interleaved data segments that the
RAID controller writes across multiple drives, not including parity drives. For example,
consider a stripe that contains 64 KB of drive space and has 16 KB of data residing on
each drive in the stripe. In this case, the stripe size is 64 KB and the strip size is 16 KB.
The user can select the stripe size.