Dell PowerEdge RAID Controller S110 - Manual (Page 13)

Features 11
Command Queuing
Command queuing is a command protocol used by SATA physical disks that
are supported by the PERC S110.
Command queuing allows the host to issue multiple input/output requests to
a disk simultaneously. The disk can then decide in which order to process the
commands to achieve maximum performance.
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 S110 adapter
utility. However, a consistency check can be 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 S110, 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.
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