Trying to understand LVM models in 4.2

[luison]

We are currently migrating one server to 4.2 and LXC and after looking at various threads I still don't have 100% clear what the new use of LVM-thin involves as far as previous storage model.

We mainly use containers with many bind mounts we've now migrated to LXC contents. We maintain LVM /pve/data mounted on /var/lib/vz where images remain as well as various other LVM LV for cache, temps, etc

By what I read I understand that PVE is pushing towards using LVM-thin for container storage which I understand means creating a thin LV dedicated for each container. I understand that this is due to snapshots working better and optimizing size used by the container disks.

My doubts are:

- can we stick for now with and "old" directory model (/pve/data/) as a storage for the containers?
- I am wrong in thinking that snapshots would still work even if slower or do live snapshots now "only" work if container is on an thin LV.
- is this any different on LXC and KVMs?
- does the thin LV "have to" exist within PVE group?


Many thanks.

 

[dietmar]

- can we stick for now with and "old" directory model (/pve/data/) as a storage for the containers?
- I am wrong in thinking that snapshots would still work even if slower or do live snapshots now "only" work if container is on an thin LV.

snapshots only work on lvm-thin

- is this any different on LXC and KVMs?

no

- does the thin LV "have to" exist within PVE group?

no

 

[luison]

Thanks.

Now to understand ho to archive the "new" default storage on an upgraded install...

I converted /pve/data like this:

lvconvert --type thin-pool pve/data

- Any issues in maintaining that mounted on /var/lib/vz while also using it for new LVM thin container storage?
- Should it or would it be better to have a different VG for this?
- To restore "old" layout containers to lvm-thin I understand I'll need to use the "-storage" flag pointing to the new named storage, can I make this become the "default" which I understand is normally "local"?