Today I performed a clean reboot, and the lockup happened just after 14 minutes of uptime. My ssh session, sftp session were locked up, so I went to the web ui and saw the CPU utilization panel details weren't moving. I had to press the power button which started a graceful shutdown, however it got stuck at this screen below. I gave it about 10 minutes before I just unplugged the server.
Things to note: Today I rebooted because I added 2 new disks. 1 for a storage pool, and 1 to expand the array. However this type of lockup has happened previously when I wasn't expanding the disks.
What's interesting is the SFTP attempted to re-connect well after the runlevel 0 happened.
Attached are the syslog reports.
graylog-search-result-relative-0.csv