What will be the value of system up time tag in PI SMT when system shuts down due to some issue?
Will it be I/O Timeout? or something else?
If you are receiving timeout even if server is running then Perfmon interface is unable to reach the counter data from the source or Interface is running with user id which is not having access to Performance monitoring group. If system is not reachable then you will see I/O timeout.
Also keep in mind, if the interface runs on the server that goes down the data won't update.
If you want to track that a server is down, I would check both if there is bad value (IO Timeout) and if the data is updated.
Retrieving data ...