New CSV Volume does not work, Event ID 5120

Problem

A newly converted Cluster Shared Volume refuses to come on-line. Cluster Validation passed with flying colours pre conversion. Looking in the event log you find this:

Log Name: System
Source: Microsoft-Windows-FailoverClustering
Date: 05.06.2016 15:01:31
Event ID: 5120
Task Category: Cluster Shared Volume
Level: Error
Keywords:
User: SYSTEM
Computer: HyperVHostname
Description:
Cluster Shared Volume ‘Volume1’ (‘VMStore1’) has entered a paused state because of ‘(c00000be)’. All I/O will temporarily be queued until a path to the volume is reestablished.

The event is repeated on all nodes.

Analysis

The crafty SAN-Admins has probably enabled some kind of fancy SAN-mirroring on your LUN. If you check, you will probably find twice the amount of storage paths compared to your usual amount. A typical SAN has 4 connections per LUN, and thus you may see 8 paths. Be aware that your results may vary. The point is that you now have more than usual. Problem is that you cannot use all of the paths simultaneously. Half of them are for the SAN mirror, and your LUNS are offline at the mirror location. If a failover is triggered at the SAN side, your primary paths go down and your secondary paths come alive. Your poor server knows nothing about this though, it is only able to register that some of the paths does not work even if they claim to be operative. This confuses Failover Clustering. And if there is one thing Failover Clustering does not like, it is getting confused. As a result the CSV volume is put in a paused state while it waits for the confusion to disappear.

Solution

You have to give MPIO permission to verify the claims made by the SAN as to whether or not a path is active. Run the following powershell command on all cluster nodes. Be aware that this is a system wide setting and is activated for all MPIO connections that use the Microsoft DSM.

Set-MPIOSetting -NewPathVerificationState Enabled

Then reboot the nodes and all should be well in the realm again.

Author: DizzyBadger

SQL DBA Principal Analyst

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