At Google Cloud Platform Live last week, we announced Sustained Use Discounts for Google Compute Engine, which automatically lower the price of your virtual machines (VMs) when you use them to run sustained workloads. You still only pay for the minutes you use, but with sustained use discounts we give you the best price for every VM you run without you having to perform any additional planning, make any long-term commitments, or pay any upfront fees. Discounts increase with use, so the more you use a VM the greater the discount you get.

We make these discounts automatically, but I’d like to take a few minutes to explain how they’re calculated and highlight some hidden benefits.

Let’s start with an example to illustrate how we calculate usage levels to give you these discounts:

Say you’re running a Web application on Compute Engine using three virtual machines. Ten days into the month, you discover potential for further optimization. You deploy a new VM with the new code, and send a small percentage of traffic to it. After running in this mode for five days, you conclude the improvements are indeed meaningful and that you only need two VMs to serve all your traffic. So you spin up a second optimized VM and shut down the original three VMs. Your customers love the improved application, and traffic grows quickly. Five days later, you spin up another VM to handle the additional traffic, and you run with these three VMs for the rest of the month.

Here’s what your usage looks like:

As you can see above, this means you have:
  • 3 VMs running for the first 10 days,
  • 4 for the next 5 days,
  • 2 for the next 5 days,
  • and 3 for the last 10 days.

We translate your usage into that pattern, which now looks like:
From a Sustained Use perspective, we treat this as exactly as above - i.e. as if you had two VMs running for 30 days (100% of the month), one running for 25 days (83.3% of the month) and one running for five days (16.7% of the month) - and we give you the appropriate discounts automatically. This approach lets us give you the greatest possible discount for a given usage pattern.

What that means for you is:
  • No lock-in or upfront minimum fee commitments
  • Greater agility (both financial and technical)
  • No complex planning required
  • No up-front payments; when you factor in the time value of money, large upfront payments are not only a source of lock-in, but also a significant hidden cost.
  • Automatically benefit from price reductions when they happen, rather than being contractually obligated to paying a rate that might, over time, be higher than the market rate.
  • No risk associated with over- or under-estimating your usage over a multi-month or multi-year period
  • No penalty for changing instance shapes as your needs change
  • Upgrade to newer instance types that may be better suited to your workload whenever you like.

With Sustained Use discounts, we’re going back to the original promises of the cloud - higher agility, simple pricing and lower risk.

- Posted by Navneet Joneja, Senior Product Manager