I didn't say it "can't" be 100tb, I said it probably shouldn't be. You can have a tlog hundreds of times the size of your database, but that doesn't make it right.

What I'm saying is, it's very abnormal for a transaction log to represent such a large percentage of the data in the database itself. That means that you have up to 100 terabytes of transactions where the data is only 800 terabytes. You can replace the tb with gb or mb or b, and it still sounds problematic. It means 1/8 of your total data is being transacted upon, based on your issue, within 50 seconds. Again, highly unusual. But then you're into the range of unusual.