I suppose it depends on which Razer Blade you have.
The 14" Razer Blade (2015) only has a single M.2 SSD slot as far as I am aware of. Maximum capacity for M.2 SSD is limited to 512GB for now.
The 17" Razer Blade has a mSATA and 2.5" SATA III slot. There are 1TB mSATA SSDs. As for 2.5" SATA III SSD... there are SSDs that have capacities up to 2TB.