freebsd stable - Mar 2017 - ZFS: vdev state changed

Hello all, I have a supermicro server with 6 2TB disk in a raidz2.
The board is a X10SRH-CLN4F with the onboard controller in IT mode. a
LSI SAS 3008

When I run a scrub I see the following in my /var/log/messages.

Feb 28 14:38:43 storage ZFS: vdev state changed,
pool_guid=11524425987729653385 vdev_guid=5999117663424576930
Feb 28 14:38:43 storage ZFS: vdev state changed,
pool_guid=11524425987729653385 vdev_guid=16120005883624137112
Feb 28 14:38:43 storage ZFS: vdev state changed,
pool_guid=11524425987729653385 vdev_guid=13065484892788124863
Feb 28 14:38:43 storage ZFS: vdev state changed,
pool_guid=11524425987729653385 vdev_guid=2891285306045195488
Feb 28 14:38:44 storage ZFS: vdev state changed,
pool_guid=11524425987729653385 vdev_guid=14130839665489078743
Feb 28 14:38:44 storage ZFS: vdev state changed,
pool_guid=11524425987729653385 vdev_guid=5801351408685715658

I do not see this on other machines. Also everything looks normal and
the scrub runs fine.
Can I found out what is causing this?

regards

Johan