After reading Adam Machanic’s comment to my previous post, I started to wonder if what I saw was all due to the fact that SQL Server blindly chooses to allocate at least one extent in response to each call to WriteToServer(), perhaps in its zeal to achieve minimal logging.   Such an algorithm sounds a bit crazy, or even dumb. But anything ...

If you have some time to kill, you could try to load a tiny amount of data, say ~3GB or 3,000,000 rows, with SqlBulkCopy, but do remember to give the WriteToServer method a very small payload every time it is called. The test results reported in my previous post suggest that once you have started loading, you might as well go for a lunch ...