Ok, so here's a weird one. I just upgraded my server hw, and everything was working fine.

Then I began tweaking stuff, and preparing to enable VMs.

I shut down docker, and moved my docker.img to /mnt/disk1/system, and reconfigured docker.

It started up fine, however most of my containers (Plex, PlexPy, Sonarr, ...) had disk I/O errors. I recreated my entire docker image two times with no effect.

 

I managed to fix it by changing all my containers' config files from /mnt/user/appdata to /mnt/disk1/appdata. However, before this was working fine, and this should be no problem according to this post: http://lime-technology.com/forum/index.php?topic=40937.msg466185#msg466185.

 

One thing I did while tweaking was turning on Tunable (enable Direct IO). Since the post I linked above mentioned FUSE, I think that might have something to do with it. I haven't tested disabling it again myself though. I've disabled it, and it did indeed fix the problem.

I've seen tunables causing some pretty funky issues in the past. Why do you want the docker.img and appdata on an array drive any way?

 

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I don't have cache drives . Anyway, I just confirmed it and submitted a bug report. Turning off direct_io and setting it back to user shares worked just fine.

You might try starting your dockers in "--privileged" mode in order to use path mapped to "mnt/user0/" or "mnt/user/" if direct i/o is turned on.