Hi everyone: Description of problem: When exec "reboot" or "shutdown -h 0" cmd on vdsm server, the vdsm server will reboot or shutdown more than 30 minutes. the screen shows '[FAILED] Failed unmouting /rhev/data-center/mnt/172.18.81.41:_home_nfs_data'. other messages may be useful: [] watchdog: watchdog0: watchdog did not stop! []systemd-shutdown[5594]: Failed to unmount /rhev/data-center/mnt/172.18.81.14:_home_nfs_data: Device or resource busy []systemd-shutdown[1]: Failed to wait for process: Protocol error []systemd-shutdown[5595]: Failed to remount '/' read-only: Device or resource busy []systemd-shutdown[1]: Failed to wait for process: Protocol error dracut Warning: Killing all remaining processes dracut Warning: Killing all remaining processes Version-Release number of selected component (if applicable): Software Version:4.2.8.2-1.el7 OS: CentOS Linux release 7.5.1804 (Core) How reproducible: 100% Steps to Reproduce: 1. my test enviroment is one Ovirt engine(172.17.81.17) with 4 vdsm servers, exec "reboot" cmd in one of the vdsm servers(172.17.99.105), the server will reboot more than 30 minutes.ovirt-engine : 172.17.81.17/16 vdsm: 172.17.99.105/16 nfs server: 172.17.81.14/16Actual results: As above. the server will reboot more than 30 minutes Expected results: the server will reboot in a short time. What I have done: I have capture packet in nfs server while vdsm is rebooting, I found vdsm is always sending nfs packet to nfs server circularly as follows:this is some log files while I reboot vdsm 172.17.99.105 in 2020-10-26 22:12:34. Some conclusion is: 1. the vdsm.log said the vdsm 2020-10-26 22:12:34,461+0800 ERROR (check/loop) [storage.Monitor] Error checking path /rhev/data-center/mnt/172.18.81.14:_home_nfs_data/02c4c6ea-7ca9-40f1-a1d0-f1636bc1824e/dom_md/metadata 2. the sanlock.log said 2020-10-26 22:13:05 1454 [3301]: s1 delta_renew read timeout 10 sec offset 0 /rhev/data-center/mnt/172.18.81.14:_home_nfs_data/02c4c6ea-7ca9-40f1-a1d0-f1636bc1824e/dom_md/ids 3. there is nothing message import to this issue.The logs is in the attachment.I'm very appreciate if anyone can help me. Thank you.