Google Compute Engine GPU and Cloud Machine Learning GPU are now available: https://cloudplatform.googleblog.com/2017/02/GPUs-are-now-available-for-Google-Compute-Engine-and-Cloud-Machine-Learning.html
Rather than constructing a GPU cluster in your own datacenter, just add GPUs to virtual machines running in our cloud. Google Compute Engine GPU are attached directly to the VM, providing bare-metal performance. Each NVIDIA GPU in a K80 has 2,496 stream processors with 12 GB of GDDR5 memory. You can shape your instances for optimal performance by flexibly attaching 1, 2, 4 or 8 NVIDIA GPUs to custom machine shapes.