error setting ACL for btsync

I'm trying to setup btsync and for this a need a shared folder where the user/group btsync has RW permissions. I have created a shared folder called syncuser and am now getting an error when setting the ACL.

Error #4000:
exception 'OMVException' with message 'Failed to execute command 'export LANG=C; setfacl --remove-all -m 'default:user:btsync:7,user:btsync:7,default:group:btsync:7,group:btsync:7,default:user::7,user::7,default:group::7,group::7,default:other::5,other::5' -- '/media/0ac8fcaa-903a-4333-9f8f-c3fe6c23a610/raumzeitfalte/btsync/users//' 2>&1': setfacl: /media/0ac8fcaa-903a-4333-9f8f-c3fe6c23a610/raumzeitfalte/btsync/users//: Operation not supported' in /usr/share/openmediavault/engined/rpc/sharemgmt.inc:1172
Stack trace:
#0 [internal function]: OMVRpcServiceShareMgmt->setFileACL(Array, Array)
#1 /usr/share/php/openmediavault/rpcservice.inc(125): call_user_func_array(Array, Array)
#2 /usr/share/php/openmediavault/rpc.inc(79): OMVRpcServiceAbstract->callMethod('setFileACL', Array, Array)
#3 /usr/sbin/omv-engined(500): OMVRpc::exec('ShareMgmt', 'setFileACL', Array, Array, 1)
#4 {main}

So what am I doing wrong? This is what I tried to apply:

So what am I doing wrong?

Okay,

well the shared folder is on an pooled drive so I guess that is the problem. Is there a way to set the permissions for btsync on a aufs. I can't choose btsync under privileges.

I found the thread you probably mean:

btsync shared folders permissions

Adding btsync to the omv group users doesn't seem like a good idea. Since then btsync has privileges everywhere the users group does. If I open the share to everyone (777 mode) does that mean that anyone with access to the can change delete everything on that share? The worst case I can think of is that somebody deletes the whole content of the share and btsync then deletes everything for the computers it sync with. Could this happen easily? My server can be reached remotely for owncloud and plex too. Is this in anyway dangerous with respect to mod 777 for the btsync share folder?