Wondering how long it would take a TOP10 Supercomputer to fully construct an 8-man tablebase.
From the bottom of this page:
Unfortunately the size of 7-man tablebases (sic. - the author means 8-man here) will be 100 times larger than size of 7-man tablebases. To fully compute them, one will need about 10 PB (10000 TB) of disk space and 50 TB of RAM. Only top 10 supercomputers can solve 8-man problem in 2014. So don't hold your breath expecting new breakthroughs too soon - the first 1000-move mate is unlikely to be found until 2020 when a part of a TOP100 supercomputer may be allowed to be used for solving this task.
This doesn't give a complete answer, but it would suggest that if you could find an estimated time for the Tianhe-2 to generate a 7-man tablebase and then multiply that result by 100, you should get a ballpark figure for the time required, probably accurate to within an order of magnitude.