At '%8' the copy of database '%1' on this server wasn't able to mount because the number of mailbox database copies on this ...

At '%8' the copy of database '%1' on this server wasn't able to mount because the number of mailbox database copies on this server exceeds the supported limit. For more detail about this failure, consult the Event log on the server for other "ExchangeStoreDb" or "msexchangerepl" events. A successful failover restored service.