becomes a hot spare with the same properties as the one it is replacing. If the replacement disk does not
match the disk protocol and technology, it does not become a hot spare.
For more information on persistent hot spares, see the Dell OpenManage documentation at dell.com/
support/manuals.
Physical disk hot swapping
NOTE: To check if the backplane supports hot swapping, see the Owner’s Manual of your system.
Hot swapping is the manual replacement of a disk while the PERC 9 series cards are online and
performing their normal functions. The following requirements must be met before hot swapping a
physical disk:
• The system backplane or enclosure must support hot swapping for the PERC 9 series cards to support
hot swapping.
• The replacement disk must be of the same protocol and disk technology. For example, only a SAS
hard drive can replace a SAS hard drive and only a SATA SSD can replace a SATA SSD.
Using replace member and revertible hot spares
The Replace Member functionality allows a previously commissioned hot spare to revert to a usable hot
spare. When a disk failure occurs within a virtual disk, an assigned hot spare (dedicated or global) is
commissioned and begins rebuilding until the virtual disk is optimal. After the failed disk is replaced (in the
same slot) and the rebuild to the hot spare is complete, the controller automatically starts to copy data
from the commissioned hot spare to the newly-inserted disk. After the data is copied, the new disk is a
part of the virtual disk and the hot spare is reverted to being a ready hot spare. This allows hot spares to
remain in specific enclosure slots. While the controller is reverting the hot spare, the virtual disk remains
optimal.
NOTE: The controller automatically reverts a hot spare only if the failed disk is replaced with a new
disk in the same slot. If the new disk is not placed in the same slot, a manual Replace Member
operation can be used to revert a previously commissioned hot spare.
NOTE: A Replace Member operation typically causes a temporary impact to disk performance.
Once the operation completes, performance returns to normal.
Controller cache preservation
The controller is capable of preserving its cache in the event of a system power outage or improper
system shutdown. The PERC 9 Series controller is attached to a Battery Backup Unit (BBU) that provides
backup power during system power loss to preserve the controller's cache data.

Cache Preservation With NVC

The Non-Volatile Cache (NVC) allows controller cache data to be stored indefinitely. If the controller has
data in the cache memory during a power outage or improper system shutdown, a small amount of
power from the battery is used to transfer the cache data to a non-volatile flash storage where it remains
until power is restored and the system is booted.
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