This test has failed rarely on master as in the past, which is why it is marked "error_ignore".
That said, it does appear that this is a steady regression on orion. I don't think this is a blocker for orion_head_sync, but we'll need to understand why the OST pools performance is significantly impacted.
More instance on Lustre b2_4 branch with FSTYPE=zfs:
https://maloo.whamcloud.com/test_sets/c11a4efc-4441-11e3-8472-52540035b04c