User's Manual

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Source RAID

Level

Target RAID Level Number of

Physical Disks

(Beginning)

Number of

Physical Disks

(End)

Capacity

Expansion

Possible

Description

disk space used

for distributed

parity data.

RAID 6 RAID 5 4 or more 4 or more Yes Removes one set

of parity data and

reclaims disk

space used for it.

RAID 6 RAID 6 4 or more 5 or more Yes Increases

capacity by

adding disks.

NOTE

: The total number of physical disks in a disk group cannot exceed 32. You cannot perform RAID level

migration and expansion on RAID levels 10, 50, and 60.

Fault Tolerance

The list of features of the PERC cards that provide fault tolerance to prevent data loss is as follows:

• Support for Self Monitoring and Reporting Technology (SMART)

• Support for Patrol Read

• Redundant path support (for PERC H810 only)

• Physical disk failure detection

• Physical disk rebuild using hot spares

• Controller Cache Preservation

• Battery and Non-Volatile Cache backup of controller cache to protect data

• Detection of batteries with low charge after boot up

The next sections describe some methods to achieve fault tolerance.

The SMART Feature

The SMART feature monitors certain physical aspects of all motors, heads, and physical disk electronics to help detect

predictable physical disk failures. SMART-compliant physical disks have attributes for which data can be monitored to

identify changes in values and determine whether the values are within threshold limits. Many mechanical and

electrical failures display some degradation in performance before failure.

A SMART failure is also referred to as a predicted failure. There are numerous factors that relate to predicted physical

disk failures, such as a bearing failure, a broken read/write head, and changes in spin-up rate. In addition, there are

factors related to read/write surface failure, such as seek error rate and excessive bad sectors.

NOTE: For detailed information on SCSI interface specifications, see t10.org and for detailed information on SATA

interface specifications, see t13.org.

Automatic Replace Member With Predicted Failure

A Replace Member operation can occur when there is a SMART predictive failure reporting on a physical disk in a

virtual disk. The automatic Replace Member is initiated when the first SMART error occurs on a physical disk that is part