you're wanting to implement a lossy compression on image files... once you do that, its done. You cannot restore it back to original quality, so just leave it in the lossy format.
performance wise this would suck man, it could be done, but it serves no purpose. Just save them in the format you want from the start.
nope, format it.
or buy a second drive to use.
Any other bastardization you come up with will likely cost you stability and, therefore, your data.
I'd say XFS, it supports fun things like defragging and such built in unlike EXT4. True that XFS can be alittle slower if you have a crap ton of tiny files, but the feature set more than makes up for it.
If you are running a newer kernel (like >= 4.4) I'd say BTRFS.
you can dual home the box, setup VLANs, or just use sshfs to connect it....
that being said, to be honest, you're doing things all wrong... the VPN thing is no reason to be running this weird setup and two LANs. Just put the VPN endpoint inside your LAN, it doesn't have to be the main router and only VPN traffic should travel across the VPN, not all internet traffic.
if you're on a budget, get used hardware... it doesn't need much cpu or ram. a 5 year old 64bit dual core (atom, celeron, or whatever) + 4GB of RAM is plenty. Just spend the money on new drives (and maybe a newer SATA controller), run RAID 6 or RAID 1 if possible (they're more reliable).
I doubt this is specific to OMV... I've seen samba do this in VMs and on metal with larger transfers.... seems to suck down about as much of a single core as it can. I'd suggest giving it a second core, but I'd expect one to get saturated during big transfers.
Why are you doing this? if it's for disk space, why not just use a filesystem that support compression on the fly?
thanks guys, I decided to go ahead with omv3... hate the idea of upgrading soon once it's declared stable 
I haven't seen any issues yet, transitioned 5TB of data so far. Honestly though, an md device with xfs is pretty stable, I really don't have a concern about losing data randomly.
so I'm new to OMV, I am not new to Linux or Debian... I have a need for a NAS, its a J1900, 4GB and 4x 4TB SATA drives (dedicated 4GB ssd boot). Right now it's running rockstor, rockstor is screwy, gui is buggy, stuff doesn't work alo, samba config is borked (had to fix config files and file permissions myself)... After the last update the newest kernel won't even boot... I'm sick of it having to dick with it. I'm either going to roll my own or try another NAS distro.
So, I was looking around, I've installed OMV2 and 3 in a virtual machine and played with it, seems good. I have no need for plugins, just NFS and maybe some SMB shares. I might, at some point, try a syncthing plugin, but I really can't imagine using any other plugins.... this is my home fileserver only.
Anyway, I'm just doing a sanity check... I am dropping rockstor due to it's screwyness, and now I'm thinking about using a beta release of OMV (yes I might have a personal issue, lol). Is OMV3 stable enough for daily use?
