Ms Windows doesnt have ZFS support. AIX also doesnt. Z/OS also. Any other commercial Linux distros don't have ZFS support. Yes you can compile it and use on production but... But PG runs on the above OS, but have check sum off by default. Thats the deal. And it is not related to ZFS existence or any other FS with checksums in any way. The question is only in performance hit when you turn it on and now I am in the process of testing it...
I don't care about those platforms, so changing the default is just making more work for me. :)
I see ;). By the way following my tests turn this option on is only 1-2% overhead in throughput.