Backup of a DC fails with the following error when the DC Storage option is configured:
"unable to execute request (113). Unable to map network share IPC$ on the computer \\FQDN\path. Multiple connections to a server or shared resource by the same user, using more than one user name, are not allowed. Disconnect all previous connections to the server or shared resource and try again."
Using the %computername% variable for the backup path (eg: \\%computername%\h$\RMADBackups) causes RMAD to try and map the share to the FQDN of the server.
OR
If the path is to a DFS share, and the 'Do not allow storage of network credentials' local security policy is enabled (https://support.microsoft.com/en-ca/help/968264/error-message-when-you-try-to-map-to-a-network-drive-of-a-dfs-share-by).
Additionally, this can be caused when using a gMSA account as the Backup Agent access account.
When this occurs, generally the issue is that the DCs are not in the security principal linked to the gMSA.
WORKAROUND 1:
Do not use the %computername% variable so that the share is not mapped using the FQDN.
For example:
Instead of using the following path for the DC Storage location:
\\%computername%\H$\RMADBackups
Use the following:
H:\RMADBackups. This will store the backups in the RMADBackups folder of the H volume on each DC in the Computer Collection.
WORKAROUND 2:
If the path in the Computer Collection is to a DFS share, and the do not store network credentials local security policy is enabled, try disabling the policy or change the path in the computer collection to just a regular windows share and not the DFS share.
NOTE: The security policy should be disabled on the Domain Controller when DC Storage is used for the RMAD backups.
