for this purpose you can add Notes when Acknowledging specific alerts (e.g. Node is Down) from the web interface.
Then you'll be able to see and export these Notes in Alert Manager GUI application (File -> Settings ->Alert View Columns)
Thanks. I am now struggling with how to connect that to my reports. Can I generate a report that says "Percent Downtime Due to Weather". I got all the % down, just need to add the filter so that I only get ones that the alert is tagged with the note Weather. ???
GZhytar, I am unable to see the notes in the alert manager GUI. The Column is there, but is empty.
The Node Details "last boot" information can help you in sorting out what lost power and what did not.
Regarding planned maintenance, you could make use of the Unmanage Scheduler so that there is no outage to account for. Backups at my datacenter were killing availability figures until I started unmanaging hundreds and hundreds of nodes during established backup cycles.
Using the Notes custom property or one that you create (ReasonForOutage) would open up lots of reporting options.
An availability report could sort or include/ exclude ReasonForOutage where WTHR_* exists or CKT_ticket_number_* exists.