There is no definitive guide that says mk1 isn't supported, but it isn't. The 250/270 all shipped with mk2 and I have never seen in in mk1...270 no question needs mk2 (for it's gbe interconnect ) and 250 is the same family. I have never seen a 250 in an mk1 and the hardware guide only shows an mk2 shelf with the 1GB/2GB switch set to 1GB for both 250/270. http://now.netapp.com/NOW/knowledge/docs/hardware/filer/210-00737_E0.pdf If you are building a FrankenFiler off support for a lab you could try the mk1 though and let us know if it works 🙂