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MegaRAID SAS Software User Guide
Chapter 2: Introduction to RAID
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Components and Features
NOTE:
In a spanned VD (R10, R50, R60) the span numbering starts from Span 0, Span 1,
Span 2, and so on.
2.4.12
Hot Spares
A hot spare is an extra, unused drive that is part of the disk subsystem. It is usually in
standby mode, ready for service if a drive fails. Hot spares permit you to replace failed
drives without system shutdown or user intervention. MegaRAID SAS RAID controllers
can implement automatic and transparent rebuilds of failed drives using hot spare
drives, providing a high degree of fault tolerance and zero downtime.
NOTE:
When running RAID 0 and RAID 5 virtual drives on the same set of drives (a sliced
configuration), a rebuild to a hot spare will not occur after a drive failure until the
RAID 0 virtual drive is deleted.
The RAID management software allows you to specify drives as hot spares. When a hot
spare is needed, the RAID controller assigns the hot spare that has a capacity closest to
and at least as great as that of the failed drive to take the place of the failed drive. The
failed drive is removed from the virtual drive and marked ready awaiting removal once
the rebuild to a hot spare begins. You can make hot spares of the drives that are not in a
RAID virtual drive.
You can use the RAID management software to designate the hot spare to have
enclosure affinity, meaning that if there are drive failures present on a split backplane
configuration, the hot spare will be used first on the backplane side that it resides in.
If the hot spare is designated as having enclosure affinity, it will attempt to rebuild any
failed drives on the backplane that it resides in before rebuilding any other drives on
other backplanes.
NOTE:
If a rebuild to a hot spare fails for any reason, the hot spare drive will be marked
as "failed". If the source drive fails, both the source drive and the hot spare drive will be
marked as "failed".
There are two types of hot spares:
Global hot spare
Dedicated hot spare
2.4.12.1 Global Hot Spare
A global hot spare drive can be used to replace any failed drive in a redundant drive
group as long as its capacity is equal to or larger than the coerced capacity of the failed
drive. A global hot spare defined on any channel should be available to replace a failed
drive on both channels.
2.4.12.2 Dedicated Hot Spare
A dedicated hot spare can be used to replace a failed drive only in a selected drive
group. One or more drives can be designated as a member of a spare drive pool. The
most suitable drive from the pool is selected for fail over. A dedicated hot spare is used
before one from the global hot spare pool.
Summary of Contents for ThinkServer RD330
Page 1: ...ThinkServer MegaRAID SAS Software User Guide ...
Page 12: ...Page 12 MegaRAID SAS Software User Guide Table of Contents ...
Page 20: ...Page 20 MegaRAID SAS Software User Guide Chapter 1 Overview Technical Support ...
Page 294: ...Page 294 MegaRAID SAS Software User Guide Chapter 8 Configuration Deleting a Virtual Drive ...
Page 386: ...Page 386 MegaRAID SAS Software User Guide Appendix A Events and Messages Event Messages ...
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