A Physical disk installation and replacement
This appendix discusses the procedure for replacing physical disks in an array.
Overview
When a physical disk fails, the logical drive it belongs to is affected. Each logical drive connected
to a Smart Array Controller can be configured with a different RAID level. Logical drives can be
affected differently by a physical disk failure, depending on their configured RAID level.
The effects of physical disk failure for each RAID level are:
RAID 0
Cannot tolerate disk drive failure. If any physical disk in the array fails, the logical
drive also fails.
RAID 1
Tolerates one physical disk failure.
RAID 1+0
Tolerates multiple physical disk failures if no failed disks are mirrored to one another.
RAID 5
Tolerates one physical disk failure.
RAID 50
Tolerates one physical disk failure per RAID 5 parity group.
RAID ADG
Tolerates simultaneous failure of two physical disks.
RAID 60
Tolerates simultaneous failure of two physical disks per RAID ADG parity group.
If more physical disks fail than the RAID level supports, fault tolerance is compromised and the
logical drive fails. All requests from the operating system are rejected with unrecoverable errors.
For steps to recover from this situation, see
“Compromised fault tolerance” (page 104)
.
SAS physical disk failure indicators (for internal disks connected to Smart
Array controllers)
The LEDs on the front of each physical disk are visible through the front of the server. When a
physical disk is configured as part of an array and is attached to a powered-on controller, you
can determine the status of the disk from the illumination pattern of the LEDs.
Figure 16 SAS Physical Disk Status LED Indicators
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102 Physical disk installation and replacement
