Improve warning about big DB on upgrade


Just upgraded to 2.1 via auto-update function. Awesome!
One thing i think that could be improved very easily:

On the DB-Update-screeen there’s a warning about updating on big DB’s… (The german text speaks about big DB, the english text about high traffic sites)
But what is big?
I’d suggest put there a rough number, that would be really easy.
And, gradually more work, maybe also output the current db-size and the php max-execution time, maybe somehow relate the two, to get a message like

“Your DB is currently 500MB, and your php execution time only 30sec. WE STRONGLY RECOMMEND TO PUT THE SITE OFFLINE BEFORE RUNNING THE UPDATE SCRIPT”