At '%8' the Exchange store database '%1' copy on this server failed to cancel a Hung IO. For more details about the failure, ...

At '%8' the Exchange store database '%1' copy on this server failed to cancel a Hung IO. For more details about the failure, consult the Event log on the server for other storage and "ExchangeStoreDb" events. If this was the active copy at the time of the error, a successful failover restored service.