Looks like ESXi 6 makes similar trouble out of the box. At least it was reported for the B120i SmartArray controller with the included -92 hpvsa driver, see Re: Very slow acces to datastores on HP MIcroserver Gen8. Can't edit System Resource Reservation with vSphere client.
A downgrade to -88 driver seems to help. So far it looks like the -90 and -92 driver version is buggy.
