You find entries in the vmkernel.log file of your ESXi hosts with the following warnings (or similar)?
Warning: CBT: 986: Unsupported ioctl 43
Warning: CBT: 2060: Unsupported ioctl 58
Unsupported ioctl numbers are only 43, 58, 59 and 60?
According to VMware KB 2058568 (ESXi host reports the error: unsupported ioctl) you can calm down.
These warning messages are harmless and can be safely ignored. They occure when certain vSCSI filters query virtual disks and some types of disks do not support ioctl request.
Just a short post, but I was a little bit terrified when I noticed hundreds of them in the logs.