Avago Technologies MegaRAID Fast Path Software - Manual (Page 30)

Page 30 LSI Corporation Confidential | July 2011
MegaRAID SAS Software User Guide Chapter 2: Introduction to RAID | Components and Features
NOTE: If a source drive fails during a rebuild to a hot spare, the rebuild fails, and the
failed source drive is marked as offline. In addition, the rebuilding hot spare drive is
changed back to a hot spare. After a rebuild fails because of a source drive failure, the
dedicated hot spare is still dedicated and assigned to the correct drive group, and the
global hot spare is still global.
An automatic drive rebuild will not start if you replace a drive during a RAID-level
migration. The rebuild must be started manually after the expansion or migration
procedure is complete. (RAID-level migration changes a virtual drive from one RAID
level to another.)
2.4.14 Rebuild Rate The rebuild rate is the percentage of the compute cycles dedicated to rebuilding failed
drives. A rebuild rate of 100 percent means that the system gives priority to rebuilding
the failed drives.
The rebuild rate can be configured between 0 percent and 100 percent. At 0 percent,
the rebuild is done only if the system is not doing anything else. At 100 percent, the
rebuild has a higher priority than any other system activity. Using 0 percent or 100
percent is not recommended. The default rebuild rate is 30 percent.
2.4.15 Hot Swap A hot swap is the manual replacement of a defective drive unit while the computer is
still running. When a new drive has been installed, a rebuild occurs automatically if
these situation occurs:
 The newly inserted drive is the same capacity as or larger than the failed drive.
 The newly inserted drive is placed in the same drive bay as the failed drive it is
replacing.
The RAID controller can be configured to detect the new drives and rebuild the
contents of the drive automatically.
2.4.16 Drive States A drive state is a property indicating the status of the drive. The drive states are
described in
Table 4 .
Table 4: Drive States
State Description
Online A drive that can be accessed by the RAID controller and is part of the virtual
drive.
Unconfigured
Good A drive that is functioning normally but is not configured as a part of a
virtual drive or as a hot spare.
Hot Spare A drive that is powered up and ready for use as a spare in case an online
drive fails.
Failed A drive that was originally configured as Online or Hot Spare, but on which
the firmware detects an unrecoverable error.
Rebuild A drive to which data is being written to restore full redundancy for a virtual
drive.