How do I turn a server and disks into a NAS capable of clustering?

I have two Dell 2650s and a 220S storage array, that is clusterable. The write performance has been so poor that Dell says many have turned to taking a server and the 220s into a NAS and clustering that way. Can it be done and how do you do this? Can Linux or Windows do this? Any direction here greatly appreciated. Most of the NAS/SAN stuff I worked with has been appliance-based.