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We have two sites, with two servers in each one.

DAC Mode (Datacenter Activation Mode) is enabled.

One peculiar thing about this network is that the Primary and the Alternate shares are set to the same value

[PS] C:\Scripts\Scripts\Windows>Get-DatabaseAvailabilityGroup -Status  | fl


Name                                   : DAG01
Servers                                : {NYCEXMB02, NYCEXMB01, TXEXMB02, TXEXMB01}
WitnessServer                          : nycexhub01.company.com
WitnessDirectory                       : c:\data\FileShareWitnessForExchange
AlternateWitnessServer                 : nycexhub01.company.com
AlternateWitnessDirectory              : c:\data\FileShareWitnessForExchange

My understanding is that the Alternate is never used unless a manual failover occurs.

That being said, we have a consistent behavior that several premier Microsoft tickets have confirmed that "shouldn't happen" but it does, wherein OWA and Outlook clients get disconnected from Exchange and simply hang.

Question

Can anyone see any reason that a 4 member DAG would hang/pause/ or dismount when two of the four nodes are unavailable, and the Quorum witness is untouched?

Additional research

I'm right now studying the implication that a two node DAG may be equivalent to a 4 node DAG, and may cause some unexpected behavior.

Log entries on active MB server

Nothing in particular is standing out, as each of these events seem to occur multiple times in the past

  • RPC request to the Microsoft Exchange Information Store service for log truncation failed for database DB05\NYCEXMB01. Error: 4294965485.

  • The program svchost.exe, with the assigned process ID 1960, could not authenticate locally by using the target name HOST/NYCEXMB01.company.com. The target name used is not valid. A target name should refer to one of the local computer names, for example, the DNS host name.

  • The OpsMgr Connector could not connect to NYCSCOMMGT.company.com:5723. The error code is 10061L(No connection could be made because the target machine actively refused it.). Please verify there is network connectivity, the server is running and has registered it's listening port, and there are no firewalls blocking traffic to the destination.

  • You should have the alternate witness not set to the same server as the witness, I don't know if that would be material to what you're seeing however. There must be something relevant in the event logs on the DAG members; have you checked? – mfinni Jul 7 '14 at 19:53
  • @mfinni - Checked the logs, nothing found... did see local connectivity issues, as mentioned above... perhaps it's a local switch issue – goodguys_activate Jul 7 '14 at 20:11

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