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Consistency check
(CC)
A consistency check is a background operation that verifies
and corrects the mirror or parity data for fault-tolerant
physical disks. It is recommended that you periodically run a
consistency check on the physical disks.
By default, a consistency check corrects mirror or parity
inconsistencies. After the data is corrected, the data on the
primary physical disk in a mirror set is assumed to be the
correct data and is written to the secondary physical disk in
the mirror set.
A consistency check cannot be user-initiated in the PERC
Virtual Disk Management utility. However, a consistency
check can user-initiated when using Dell OpenManage Server
Administrator Storage Management.
Disk initialization For physical disks, initialization writes metadata to the
physical disk, so that the controller can use the physical disk.
Fault tolerance The following fault tolerance features are available with the
PERC S100 adapter and PERC S300 adapter, in order to
prevent data loss in case of a failed physical disk:
• Physical disk failure detection (automatic).
• Virtual disk rebuild using hot spares (automatic, if the hot
spare is configured for this functionality).
• Parity generation and checking (RAID 5 only).
• Hot-swap manual replacement of a physical disk without
rebooting the system (only for systems with a backplane that
allows hot-swapping).
If one side of a RAID 1 (mirror) fails, data can be rebuilt by
using the physical disk on the other side of the mirror.
If a physical disk in RAID 5 fails, parity data exists on the
remaining physical disks, which can be used to restore the
data to a new, replacement physical disk configured as a hot
spare.
If a physical disk fails in RAID 10, the virtual disk remains
functional and data is read from the surviving mirrored
physical disk(s). A single disk failure in each mirrored set can
be sustained, depending on how the mirrored set fails.
Table 3-1. Features of the PERC S100 controller and PERC S300 controller
(continued)
RAID Controller Feature Description
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