Can you expand on that read-only problem a little more... The mnt/ssd is probably because you're mounting an ssd drive through the unassigned devices plugin.
Entirely possible if not for the fact that there's only 1 ssd in the server and i don't have the unassigned devices plugin
Also, when i create the img in /mnt/ssd/ the number of writes on the cache ssd increases.
Scenario:
I turned Docker on, put the img in /mnt/cache/, added the Lime-Tech Plex container, tried to add a second container and then i got a similar error to this one,
https://lime-technology.com/forum/index.php?topic=42932.0
I came across the above topic, deleted the img, recreated it again in /mnt/cache/, added the Lime-Tech Plex container, tried to add a second container and then the error happened again. Then tried the same thing all over again but started with a different container and same result. Several variations of this happened when i noticed the /mnt/ssd/ share, wrote the image to that and haven't had a problem since.
And i was about to end my comment on that note when i thought "lets try adding a container".
Tried to add l3iggs Owncloud container,
Full log, https://mega.nz/#!ilVjxIbB!5qFiIZrUwGkbrpcMg0XW4TPFQ8LvaoS4kZ5zbQbupIk
I'dd add Diagnostics but that results in: 404 File not found