Amazon EC2 的 r4.* 總算是開出來了：「Amazon EC2 R4 instances are now available in new regions」。
Amazon EC2 R4 instances are now available in the following regions: Asia Pacific (Tokyo), Asia Pacific (Singapore), South America (São Paulo), Asia Pacific (Seoul), Asia Pacific (Mumbai), Canada (Central), and EU (London).
r4.16xlarge (488GB) 算是補上中間的 r3.8xlarge (244GB) 與 x1.16xlarge (976GB) 中間的一塊洞了，不然之前得開 p2.8xlarge (488GB)，但也不是每一區都有，而且用不到 GPU 就浪費了...