It seems that you used the backup utility built within WIndows 7 and not the Connector Software that comes with WD Sentinel DX4000.
As GHoward mentioned … When using the Connector Software on your Windows machine, “The client backup automatically switches to incremental after the first full backup.”
By default the backups are full/bare-metal backup and every subequent backup is much faster since it only copies over incremental “blocks”. Thanks to Block level deduplication, built into the backup technology that WD Sentinel provides via Windows Storage Server 2008 R2 Essentials OS.
Quite often the bottleneck can be the networking equipment, which might be dated:
- I tend to avoid having a laptop on Wi-fi, at least for the first backup.
- If your router is somewhat old i.e. 802.11g, that can contribute to a lower throughput
- Similarly the LAN connectivity, whether your router/switch provdies Gigabit connectivity or not.
Hope this helps!