OpenZFS on OS X

I built/installed from the latest source as of today and allowed OpenZFS to upgrade my pool (probably a bad idea) anyhow, ever since then I'm showing kernel_task using around 7GB of ram (about double what it used to) and over the last few hours it's written about 41GB to disk (the computer has been sitting idle this whole time with nothing running on it). Also eventually IO tasks to the zpool start hanging for very long periods of time, occasionally indefinitely.

I have re-disabled spotlight on the volume so that's not it. Any ideas?

Well it seems to have been part of the pool upgrade process, after letting it sit for ~8 hours it's finally done and my computer slowly seems to be returning to normal.

Have a look in /var/log/system_log, in particular look for the drain lines.

# grep drain /var/log/system_log

Older version of o3x did not remove xattrs, so now we do, which mean the first import might be very long. We will warn about this in the installer
On the plus size, you just got a bunch of space back.

Yup, that was indeed it. On the plus side I've noticed some performance improvements and of course Spotlight is very nice