how does your /etc/vzdump.conf look like
also what is the exact command line which you call for the backup?
INFO: starting new backup job: vzdump 101 --mode snapshot --remove 0 --compress 0 --storage diskTwo --node server3
INFO: filesystem type on dumpdir is 'zfs' -using /var/tmp/vzdumptmp12661 for temporary files
proxmox-ve: 4.1-39 (running kernel: 4.2.8-1-pve)
pve-manager: 4.2-5 (running version: 4.2-5/7cf09667)
pve-kernel-4.2.6-1-pve: 4.2.6-36
pve-kernel-4.2.8-1-pve: 4.2.8-41
lvm2: 2.02.116-pve2
corosync-pve: 2.4.0-1
libqb0: 1.0-1
pve-cluster: 4.0-33
qemu-server: 4.0-85
pve-firmware: 1.1-8
libpve-common-perl: 4.0-71
libpve-access-control: 4.0-18
libpve-storage-perl: 4.0-56
pve-libspice-server1: 0.12.8-1
vncterm: 1.2-1
pve-qemu-kvm: 2.6-1
pve-container: 1.0-71
pve-firewall: 2.0-29
pve-ha-manager: 1.0-33
ksm-control-daemon: 1.2-1
glusterfs-client: 3.5.2-2+deb8u2
lxc-pve: 1.1.5-7
lxcfs: 2.0.0-pve2
cgmanager: 0.39-pve1
criu: 1.6.0-1
zfsutils: 0.6.5.7-pve10~bpo80
please update your installation, there have been some bugfixes regarding vzdump
also pigz cannot work if you specify "--compress 0" it has to be "--compress gzip"
apt-get dist-upgrade
apt-get upgrade
apt-get update
apt-get dist-upgrade
The tmpdir is only filled in suspend mode backups, you seem to be using snapshot mode.