Dell Shared PowerEdge RAID Controller 8 Cards For Dell PowerEdge VRTX Systems User’s Guide

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Controller cache issues

For certain conditions virtual drives are either not configured to write back caching or if configured, it transitions to write-through caching. The status of write-back caching can be viewed through CMC storage logs.

The following table details the conditions and the corrective actions.

Table 1. Conditions and the corrective actions . This table describes the conditions and the corrective actions.
Conditions	Actions
Peer controllers reporting incompatibility due to mismatched controller settings	When the active controller does not have any native configurations and imports a foreign configuration, the active controller inherits the controller configuration settings stored with the virtual disk. These settings may differ from the settings present on the peer controller, which triggers the incompatibility due to controller setting mis-match. It is recommended to manually reconcile the difference in settings to resolve the issue.
During the VRTX power on with no failing conditions, the virtual drive temporarily transitions to write-through as part of the Shared PERC 8 firmware initialization. After the system power-on, the virtual drive transitions back to write back.	There is no intervention required.
During VRTX power on or reset, unresolved pinned cache is present. NOTE: If a Reset Configuration action is performed in CMC while pinned cache is present, the cache will be cleared and the data will not be recoverable. NOTE: Unresolved pinned cache can occur if a virtual drive goes offline for any reason while there is uncommitted cache data in memory. NOTE: When pinned cache is present, the controller failover feature will not occur. Pinned cache must be addressed before controller failover is allowed.	Perform the following: Insert the drives that caused the virtual drive to go offline, that resulted in the cache being pinned to recover the virtual drive. OR Clear the pinned cache through CMC. NOTE: Clearing pinned cache means that the pinned data is lost.
During a Shared PERC firmware flash, virtual drive transitions to write-through until chassis is recycled.	Allow the chassis reset to complete after the firmware flash.
Virtual drives permanently transition to write-through when the Hardware failure occurs.	If hardware failure occurs, contact Dell technical support. For more information, see the Getting help.
In the event of a firmware mismatch, in the dual fault tolerant Shared PERC 8 configurations, if one controller has write-through capability and the other does not, virtual drives on the controller with write-through capability reverts to write-through.	Update the firmware such that both cards are running the latest supported versions available. NOTE: Ensure that you download the updated firmware and driver version available at Dell.com/support/home.

NOTE: Virtual drives configured with forced write-back caching are not transitioned to write-through in the above conditions.