Avago Technologies MegaRAID SATA 150-4 (523) - Manual (Page 32)

2-10 Introduction to RAID
Copyright © 2003–2006 by LSI Logic Corporation. All rights reserved.
The RAID management software allows you to specify physical 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 replace the failed drive. The failed drive is removed
from the logical drive and marked ready awaiting removal after the
rebuild to a hot spare begins. See Table 2.13 for detailed information
about the minimum and maximum number of physical drives supported
by each RAID level for each RAID controller. You can make hot spares
of the physical drives that are not in a RAID logical drive.
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.
There are two types of hot spares:
•
Global Hot Spare
•
Dedicated Hot Spare
2.4.12.1 Global Hot Spare
A global hot spare can replace any failed drive in a redundant array 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 replace a failed drive only in a selected array.
One or more drives can be designated as member of a spare drive pool;
the most suitable drive from the pool is selected for failover. A dedicated
hot spare is used before one from the global hot spare pool.
Hot spare drives can be located on any RAID channel. Standby hot
spares (not being used in RAID array) are polled every 60 seconds at a
minimum, and their status is made available in the array management
software. RAID controllers can rebuild with a disk that is in a system, but
not initially set to be a hot spare.
Observe the following parameters when using hot spares: