Please correct me if this is not a bug but it sure looks like one.  I upgraded to V6 about a month ago from V5.0.3 with a Pro license using the procedure defined by LT (copying some config from the old flash to re-formatted one).  I'm currently running V6.0rc3.  I stopped the array to do a little maintenance and noticed the "Cache Devices" tab for the first time in V6.  I'm not currently using a cache drive but did briefly a very long time ago.  I noticed that the number of cache drive slots was set to 1 and the assigned device was set to "unassigned".  Since I'm not using a cache drive I changed the "slots" to "none" and when I started the array I had a /mnt/user0.

If you reboot that should go away; will fix in next release.

The reboot did not fix the issue on my system. I had to edit manually /boot/config/share.cfg and modify it like this:

 

shareCacheEnabled="yes" (change to "no")

shareMoverLogging="yes" (changed to "no" since the previous line disables caching)

 

And now it works.