Avago Technologies MegaRAID Fast Path Software - Manual (Page 28)

Page 28 LSI Corporation Confidential | July 2011
MegaRAID SAS Software User Guide Chapter 2: Introduction to RAID | Components and Features
2.4.11.1 Spanning for RAID 00,
RAID 10, RAID 50, and RAID 60 Table 3 describes how to configure RAID 00, RAID 10, RAID 50, and RAID 60 by
spanning. The virtual drives must have the same stripe size and the maximum number
of spans is 8. The full drive capacity is used when you span virtual drives; you cannot
specify a smaller drive capacity.
See Chapter 8, Configuration for detailed procedures for configuring drive groups and
virtual drives, and spanning the drives.
NOTE: In a spanned virtual drive (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.
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 after
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 drive failures are present on a split backplane
configuration, the hot spare will be used first on the backplane side in which it resides.
If the hot spare is designated as having enclosure affinity, it attempts to rebuild any
failed drives on the backplane in which it resides before rebuilding any other drives on
other backplanes.
NOTE: If a rebuild to a hot spare fails for any reason, the hot spare drive is marked as
failed. If the source drive fails, both the source drive and the hot spare drive are marked
as failed.
Table 3: Spanning for RAID 10, RAID 50, and RAID 60
Level Description
00 Configure RAID 00 by spanning two contiguous RAID 0 virtual drives, up to
the maximum number of supported devices for the controller.
10 Configure RAID 10 by spanning two contiguous RAID 1 virtual drives, up to
the maximum number of supported devices for the controller. RAID 10
supports a maximum of 8 spans. You must use an even number of drives in
each RAID virtual drive in the span. The RAID 1 virtual drives must have the
same stripe size.
50 Configure RAID 50 by spanning two contiguous RAID 5 virtual drives. The
RAID 5 virtual drives must have the same stripe size.
60 Configure RAID 60 by spanning two contiguous RAID 6 virtual drives. The
RAID 6 virtual drives must have the same stripe size.