Hey Jonathon --
#1: On Tableau Server Perf Recordings, things are measured based on the number of seconds it's been since the VizQLServer process has been running. So, for a newly restarted Tableau Server, your time scale might start at "10" - essentially 10 seconds since the service started. If your Server has been running for days, your starting value will be a big value since the vizQLServer in question has been running for "many seconds". I don't think you'll ever see "0" as your start time in a Server Performance report because you're just not ever going to be fast enough to hit a VizQLServer process with a request at the moment it comes to life.
#2. No. The report shows what happened to render this specific report by the specific user who ran it. That's why you append the :record_performance=yes parameter to the end of a specific report vs. just going into an admin area somewhere and click a "start performance recording now" button, then turning it off again after a while. The feature is there to help you troubleshoot why a specific report isn't fast - not as a way to audit performance across multiple reports at a stretch. That would be way too much data to sift through.
I don't understand #3 - can you add more context to your question?
As always thanks for your response! Disappointing but helpful. I was hoping the performance data would be a bit more robust for my purposes.
#3 - To clarify, when I view the performance recording report it doesn't quite jive with my experience when interacting with reports. For example, it may show that it took 1 second to connect data and another 2 seconds for the query (these are just hypothetical times), but when I actually open the report in my browser it may take 10 seconds for the report to load. I understand that the performance recording is only measuring what Tableau is doing not necessarily bandwidth and other factors, but the differences are usually large. Although perhaps I am missing something.
Let me know if this helps.
Thanks - And you already pretty much answered the question for yourself
You're 100% correct in that we're only "watching" the Tableau rendering process. There are lots of other things going on that we're not measuring - like how long it takes to pull the XML definition of the report out of our internal database, how long it takes to "bootstrap" a VizQL session, how long it takes to send data across the wire to your browser, and so on.
Some of this extra time you might be able to measure with things like the built-in Chrome/IE Developer tools, FireFox's Firebug, etc.