Physical disk failure detection
Failed physical disks are detected and rebuilds automatically start to new disks that are inserted into the
same slot. Automatic rebuilds can also occur with hot spares. If you have configured hot spares, the
controllers automatically try to use them to rebuild failed physical disks.
Physical Disk Hot Swapping
NOTE: Shared PERC 8 supports physical disk hot-swapping, however this should only be
implemented for unconfigured or failed drives.
Hot swapping is the manual replacement of a disk while the Shared PERC 8 card is online and performing
the normal functions. The following requirements must be fulfilled before performing a hot swap of a
physical disk:
• 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.
• The replacement disk must be of equal or greater capacity than the one it is replacing.
Auto Replacement Of A Virtual Disk Member And Revertible Hot Spares
The automatic Replace Member functionality allows a previously commissioned hot spare to be reverted
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 physical disk
is replaced (in the same slot) and the rebuild is complete, the Shared PERC 8 card 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 a ready hot spare. This allows hot spares to
remain in specific enclosure slots. While the Shared PERC 8 card is reverting the hot spare, the virtual disk
remains optimal.
NOTE: The Shared PERC 8 card automatically reverts a hot spare only if the failed disk is replaced
with a new disk in the same slot.
NOTE: A Replace Member operation typically has a temporary impact on disk performance. After
the operation completes, the disk performance returns to normal.
Shared PERC 8 Card Cache Preservation
The Shared PERC 8 card is capable of preserving its cache in the event of a system power outage or
improper system shutdown. The Shared PERC 8 card is attached to a Battery Backup Unit (BBU) that
provides backup power to transfer contents of the DRAM to the Non-Volatile Cache (NVC) during system
power loss.
NOTE: The Controller Cache Preservation feature is applicable only for virtual disks in write-back
mode. Virtual disks in write-through mode do not have any data in cache.

Cache Preservation With Non-Volatile Cache

The Cache Preservation With Non-Volatile Cache (NVC) module 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 cache data to a non-
volatile flash storage where it remains until power is restored and the system is booted.
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