BernieT wrote a nice blog about why you should enable write cache. Check out his findings, below a short outtake.
Explaining Write mode (basic’s).
Write through -> When a write request is received by the RAID controller, the controller will not respond to the O/S with a “write success” until the data is written to the physical disk/s.Write back –> When a write request is received by the RAID controller, the controller will cache the request/data and respond to the O/S with a “write success”, then write the data to the physical disk/s.