Not understanding what lvm-thin is used for

[camrunr]

I'm trying to replace my FreeNAS system with Proxmox. The plan is to leave the NAS duties on FreeNAS for now, and migrate all the FreeNAS jails' services over to pve. So far I'm in discovery mode. I installed a fresh LXC from the ubuntu template. I mounted the NFS share for my media library at the host level, and then a bind mount point to see that mount inside the LXC container. I plan on using docker containers inside the LXC for each of the services. I noticed at this point that pve only used about 60 GB of the SSD I installed on. The rest is allocated to LVM-thin, which has no obvious functionality in the GUI.

How can I make use of this space for the docker containers' persistent storage?

EDIT: Updated layout. Comments?

Overall layout:
- FreeNAS for media share
- 2 pve hosts running a turnkey-core LXC container (HP ProDesk 600 G4, 16GB, 6core, 250 GB)
- each LXC is running multiple docker containers for the various services I use
- the hosts both NFS mount my media share from FreeNAS, and pass through to containers as volume binds

 

[t.lamprecht]

The rest is allocated to LVM-thin, which has no obvious functionality in the GUI.

This is done when using the defaults in the installer and its size can be controlled vai the maxvz option there, see:
https://pve.proxmox.com/pve-docs/chapter-pve-installation.html#advanced_lvm_options

The LVM-Thin serves as default storage for VM/CT volumes, it allows cheap snapshots and is flexible in general. In Proxmox VE's API/GUI the default LVM-Thin created on installation will shop up as "local-lvm" storage and can be used for allocating guest images as other storage can.

How can I make use of this space for the docker containers' persistent storage?

Add a mount point to the container (CT -> Resources -> Add) and select local-lvm as backing storage for the new volume.
You may also want to read/skim the docs alongside your evaluation, e.g., the PVE storage system chapter for this one:
https://pve.proxmox.com/pve-docs/chapter-pvesm.html