Important: Spot VMs are the latest version of preemptible VMs, andwe recommend using Spot VMs instead of preemptible VMs. New andexisting preemptible VMs continue to be available,and preemptible VMs use the same pricing model as Spot VMs. However,Spot VMs provide new features that preemptible VMs don't support.For example, preemptible VMs can only run for up to 24 hours at a time, butSpot VMs don't have a maximum runtime unless youlimit the runtime. Learn more aboutSpot VMs andhow tocreate Spot VMs.

This page describes preemptible virtual machine (VM) instances. To learn how tocreate a preemptible instance, readCreate and use preemptible VMs.To learn more about instances in general, read theVirtual machine instances documentation.

What is a preemptible instance?

Preemptible VM instances are available at muchlower price—aup to 91% discount—compared to theprice of standard VMs.However, Compute Engine might stop (preempt) these instances ifit needs to reclaim the compute capacity for allocation to other VMs. Preemptibleinstances use excess Compute Engine capacity, so their availabilityvaries with usage.

If your apps are fault-tolerant and can withstand possible instancepreemptions, then preemptible instances can reduce your Compute Enginecosts significantly. For example, batch processing jobs can run on preemptibleinstances. If some of those instances stop during processing, thejob slows but does not completely stop. Preemptible instances complete yourbatch processing tasks without placing additional workload on your existinginstances and without requiring you to pay full price for additional normalinstances.

Preemptible instance limitations

Preemptible instances function like normal instances but have thefollowing limitations:

• Compute Engine might stop preemptible instances at any time dueto system events. The probability that Compute Engine stopsa preemptible instance for a system event is generally low, but might vary fromday to day and from zone to zone depending on current conditions.
• Compute Engine always stops preemptible instances after theyrun for 24 hours.Certain actions reset this 24-hourcounter.
• Preemptible instances are finite Compute Engine resources,so they might not always be available.
• Preemptible instances can'tlive migrateto a regular VM instance, or be set toautomatically restartwhen there is a maintenance event.
• Due to the preceding limitations, preemptible instances are not covered by anyService Level Agreement and are excluded from theCompute Engine SLA.
• TheGoogle Cloud Free Tier credits forCompute Engine do not apply to preemptible instances.

Preemption of preemptible VMs

This section describes how preemptible VMs are preempted byCompute Engine and which VMs are selected for preemption.

Preemption process

Compute Engine performs the following steps topreempt an instance:

1. Compute Engine sends a preemption notice to the instance in theform of anACPI G2 Soft Off signal. You can use ashutdown scriptto handle thepreemption notice and complete cleanup actions before the instance stops.The shutdown period for a preemption notice is best effort and up to30 seconds.
2. If the instance has not stopped after the shutdown period for the preemptionnotice, Compute Engine sends anACPI G3 Mechanical Off signal to the operating system.
3. Compute Engine transitions the instance to aTERMINATED state.

You can simulate an instance preemption bystopping the instance.

Preempted instances still appear in your project, but you are not charged forthe instance hours while it remains in aTERMINATED state. You can access andrecover data from any persistent disks that are attached to the instance, butthose disks still incur storage charges until you delete them. As with normalinstances, persistent disks that are marked for auto-delete are deleted when youdelete the preemptible instance. You can restart a preempted instance as manytimes as you would like, as long as there is capacity. Restarting a preemptibleinstance resets the preemptible process.

If Compute Engine stops a preemptible instance less than oneminute after it is created, you are not billed for the use of that VM instance.This ensures that you don't pay for preemptible instances unless they have hadtime to complete a significant amount of work. However, the charges forpremium operating systems are still calculatedas normal.

Preemption selection

See ourbest practicesfor suggestions on reducing your preemption rate. Note that Compute Enginedoesn't charge you for instances if they are preempted in the first minuteafter they start running.

Certain actions reset the 24-hour counter for preemptible instances.Specifically, if youstopandstartan instance, Compute Engine resets the counter because theinstance transitions into aTERMINATED state. However, other actions, wherethe instance remains inRUNNING state, don't reset the counter, for example,resetting or rebooting an instance.

Pricing

Preemptible VMs use spot prices, the same pricing model as Spot VMs.For more information about the pricing of preemptible VMs, seepricing for Spot VMs.

Using preemptible VMs with Compute Engine

This section provides notable information about using preemptible VMs withother Compute Engine offerings. Learn about using preemptible VMswith managed instance groups, premium operating systems, local SSDs, and GPUs.Additionally, understand how preemptible VMs affect your quotas forCompute Engine resources.

Preemptible instances in a managed instance group

You can create preemptible instances in amanaged instance group. Specifythe preemptible option in theinstance template before you create orupdate the group.

Managed instance groups can create or add new preemptible instances onlywhen additional Compute Engine resources are available. If theseresources are limited, managed instance groups are unable to resize orautomatically scale the number of preemptible instances in the group.

Managed instance groups always attempt to maintain their target size or the sizespecified by theautoscaler for that group. IfCompute Engine stops a preemptible instance in a managed instancegroup, the group repeatedly tries to recreate that instance using the specifiedinstance template. If the necessaryresources become available again, the group recreates the instance and maintainsthe target group size.

Premium operating systems on preemptible instances

Preemptible instances don't reduce the cost ofpremium operating systems anddon'tchange the way that you're billed for the use of those operating systems. IfCompute Engine stops a preemptible instance that runs a premiumoperating system, you are billed for that operating system as if you stoppedthe instance yourself. The charges for minimum usage still apply, and bills forpremium operating systems are still calculated by rounding up to the nearestusage increment.

The machine types on preemptible instances that run premium operating systemsare always billed by the second, and follow the prices listed on theVM instance pricing page.

Local SSDs on preemptible instances

If you start aSpot VM or preemptible VMwith a Local SSD disk, Compute Engine charges discountedspot pricesfor the Local SSD usage. Local SSD disks that are attached to Spot VMs orpreemptible VMs work like normal Local SSD disks, retain the samedata persistence characteristics,and remain attached for the life of the VM.

Compute Engine doesn't charge you for Local SSD disk usage on aSpot VM or preemptible VM if the VM is preempted within a minute after itstarts running.

GPUs on preemptible instances

You can add GPUs to your preemptible VM instancesat lowerspot prices for the GPUs. GPUsattached to preemptible instances work like normal GPUs but persist only forthe life of the instance. Preemptible instances with GPUs follow the samepreemption processas all preemptible instances.

Consider requesting dedicatedPreemptible GPU quota to use for GPUs onpreemptible instances. For more information, seeQuotas for preemptible VM instances.

During maintenance events, preemptible instances with GPUs are preempted bydefault and cannot be automatically restarted. If you want to recreate yourinstances after they have been preempted, use amanaged instance group.Managed instance groups recreate your instances if the vCPU, memory, andGPU resources are available.

If you want a warning before your instance is preempted, or want to configureyour instance to automatically restart after a maintenance event, use astandard instance with a GPU. For standard instances with GPUs,Google providesone hour advance noticebefore preemption.

Compute Engine does notcharge you for GPUs if their instances are preempted in the firstminute after they start running.

For steps to automatically restart a standard instance, seeUpdating options for an instance.

To learn how to create preemptible instances with GPUs attached, readCreate a VM with attached GPUs.

Quotas for preemptible VM instances

Like other VMs, preemptible VMs require availableCPU quotas. Additionally, if you planto use preemptible VMs with local SSDs or with GPUs, preemptible VMsalso requiredisk quota andGPU quota respectively.

If you use preemptible VMs with these resources and have notrequested preemptible quota, then preemptible VMs consume yourstandard quota for these resources.If you plan to use preemptible VMs, consider requestingpreemptible quota for those resources to prevent preemptible VMs fromconsuming your quotas.

After Compute Engine grants you preemptible quota in a region, allpreemptible VMs (and anySpot VMs)in that region count against that quota. All standard VMs inthat region continue to count against the standard quota. In regions where youdon't have preemptible quota, you can use standard quota to launch preemptible VMs.

Note: Once you request preemptible quota in a region, you are limited to usingthat quota for preemptible VMs in that region. You can't consumestandard quota in its place.

Preemptible quota is not visible in the gcloud CLI orGoogle Cloud console quota pages unless Compute Engine has grantedthe quota. For more information, seeAllocation quotas for preemptible resources.

What's next?

• Create and use preemptible VMs.

Try it for yourself

If you're new to Google Cloud, create an account to evaluate how Compute Engine performs in real-world scenarios. New customers also get $300 in free credits to run, test, and deploy workloads.

Try Compute Engine free