HP Smart Array 6400 Series Controllers Support Guide, September 2007

B Physical Disk Installation and Replacement
This appendix discusses the procedure for replacing physical disks in an array. This appendix
addresses the following topics:
“Overview” (page 67)
“Physical Disk Failure” (page 67)
“Compromised Fault Tolerance” (page 70)
“Automatic Data Recovery” (page 70)
“Physical Disk Replacement Overview” (page 71)
“Physical Disk Failure During Rebuild” (page 71)
Overview
Each SCSI channel on a Smart Array Controller can support up to 14 physical disks. Disks can
be Ultra320 or Ultra160.
Each physical disk on a SCSI bus must have a unique ID value from 0 to 15 (except ID 7, which
is reserved for controller use). This value is set automatically on hot-pluggable disk drives in the
storage systems that are supported by the Smart Array 6400 Series Controller.
When replacing disk drives, consider the following:
• Do not terminate the disk drives. HP servers and internal cabling provide the required
termination of the SCSI bus.
• Do not use disk drives with different capacities in the same array. The excess capacity of
larger disk drives cannot be used by the array and is wasted.
• Do not use hot-pluggable and non-hot-pluggable disk drives on the same SCSI bus.
Physical Disk Failure
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 ADG Tolerates simultaneous failure of two physical disks.
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 to recover from this situation, see “Compromised Fault Tolerance” (page 70).
Recognizing Disk Failure
The LEDs on the front of each physical disk are visible through the front of the StorageWorks
disk and MSA 30 enclosures. When a physical disk is configured as part of an array and attached
to a powered-on controller, you can determine the status of the disk from the illumination pattern
of the LEDs.
Figure B-1 illustrates a typical set of status LEDs. Table B-1 describes the meanings of the LED
combinations.
Overview 67