Thank you for your response.
I am sorry about the vague question.
Actually my NVR showing the alert correctly, when I unplug the HDD it shows 'No HDD' message.
I need to get all the events using an API. I see that it is possible by using the url ip/cgi-bin/eventManager.cgi?action=attach&codes=[AlarmLocal etc...].
In this I am not able to get the HDD failure alerts. I am able to see it in the log which can be fetched using the url action=startFind&condition.StartTime=2017-5-10 12:00:00&condition.EndTime=2017-5-10 15:00:00 and doFind.
I am not able to get the HDD alerts using the eventManager API, is it possible? Or do I need to use any other API like log.cgi to get the same ?
Bit more info might help. Model numbers, symptoms etc.
Dahua NVRs do a S.M.A.R.T. check - is that failing?