I installed RC1 and it booted fine. Dockers & VM's running. Hit the Stop button to bring down the array so I could change a SMB setting to disable netbios. The status bar kept reporting that it was retrying to unmount. Unable to pull up the syslog via the GUI so I telnetted in and tailed the syslog. Received the following over & over.
Oct 15 01:17:30 NAS emhttpd: Retry unmounting disk share(s)...
Oct 15 01:17:35 NAS emhttpd: Unmounting disks...
Oct 15 01:17:35 NAS emhttpd: shcmd (250): umount /mnt/cache
Oct 15 01:17:35 NAS root: umount: /mnt/cache: target is busy.
Oct 15 01:17:35 NAS emhttpd: shcmd (250): exit status: 32
lsof didn't report any files on /mnt/cache open. "mount -l" reported:
/mnt/cache/system/docker/docker.img on /var/lib/docker type btrfs (rw)
I entered "umount /var/lib/docker" and the unraid "Stop" function was able to complete.
Seems like the unmount order needs to be adjusted.