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Google Offers 'Preemptible' Virtual Machines

They're cheap, but can be shut down without warning, and are automatically terminated after 24 hours.

If you don't mind running a virtual machine (VM) that will live for just 24 hours, and can be shut down with only 30 seconds advance notice, then Google Inc. might have a great deal for you.

It's offering Google Compute Engine Preemptible Virtual Machines, a short-lived VM type that's in beta right now, according to a post on the Google Cloud Platform Blog. "Preemptible VMs are the same as regular instances except for one key difference -- they may be shut down at any time," wrote Paul Nash, a Google senior product manager.

Fixed Pricing -- for a Price
By not giving a guarantee that the VM will be available, Nash said, Google can fix pricing for it, allowing a company to have more predictable costs. He said prices will start at $0.01 per core hour.

That low price comes attached with strings the size of skyscrapers, however. For one, the VM's runtime is limited to 24 hours. And, if Google should need the space or resources being occupied by that VM, the VM will be terminated without prejudice.

That's why Google says the best types of applications for these VMs are fault tolerant and can afford to be interrupted. It provides an example of batch processing jobs within the documentation page: "If some of those instances terminate during processing, the job slows but does not completely stop."

Terminated Without Prejudice
Google adds that the probability that a running VM will be shut down is "generally low," but it will probably happen from time to time. And those VMs will be terminated after running for 24 hours, no matter what.

There are two other important caveats:

  1. In some instances, it may not even be possible to create a preemptible VM; it depends on whether Google has Compute Engine resources available.
  2. Preemptible VMs can't live migrate, so if it's shut down, it won't be spinning back up on another host.

Nash blogged that preemptible VMs can be created through the Google Developer Console, or by adding "--preemptible" to the gcloud command line. A Google pricing page shows that some of its cheapest per-hour VM charges can range anywhere between $0.03 per hour, up to $0.11 per hour or more. Thus, the Preemptible VMs could result in a substantial savings -- for the right workload.

About the Author

Keith Ward is the editor in chief of Virtualization & Cloud Review. Follow him on Twitter @VirtReviewKeith.

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