Redundant path with load balancing support, Using replace member and revertible hot spares, Redundant path with load – Dell PowerEdge RAID Controller H800 User Manual
Page 35: Balancing support, Using replace member and, Revertible hot spares
Storage Controller Features
35
Redundant Path With Load Balancing Support
The PERC H800 adapter can detect and use redundant paths to disks
contained in enclosures. This provides the ability to connect two SAS cables
between a controller and an enclosure for path redundancy. The controller is
able to tolerate the failure of a cable or Enclosure Management
Module (EMM) by utilizing the remaining path.
When redundant paths exist, the controller automatically balances I/O load
through both paths to each disk. Load balancing increases throughput to
virtual disks in storage enclosures and is automatically turned on when
redundant paths are detected. The ability to load balance I/O can be disabled
using the Dell OpenManage storage management application. To set up your
hardware to support redundant paths, see "Setting up Redundant Path
Support on the PERC H800 Adapter" on page 64.
NOTE:
The hardware support for redundant paths refer to path-redundancy only
and not to controller-redundancy.
Using Replace Member and Revertible Hot Spares
The 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 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.
PERC7.2_UG.book Page 35 Thursday, March 3, 2011 2:14 PM