Spot VMs
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This page describes Spot VMs:
virtual machine (VM) instances that are excess
Compute Engine capacity. Spot VMs have significant discounts,
but Compute Engine might preemptively stop or delete (preempt)
Spot VMs to reclaim the capacity at any time. Spot VMs
are the latest version of
preemptible VMs.
Specifically, Spot VMs are VMs that use the spot provisioning model.
The provisioning model of a VM
affects its discounts and availability. The spot provisioning model lets you
obtain resources at much lower prices compared to standard VMs. However,
Compute Engine can preempt Spot VMs at any time to reclaim
resources. Use Spot VMs to reduce costs for fault-tolerant workloads,
such as batch processing jobs or stateless applications.
What are Spot VMs?
Spot VMs are available at much lower
prices—up to 91% discounts for many machine types, GPUs, TPUs,
and Local SSDs—compared to the on-demand price for standard VMs.
However, Compute Engine might preempt Spot VMs at any time,
such as when it needs the resources for other tasks. At this uncertain
preemption time, Compute Engine either stops (default) or deletes your
Spot VMs depending on your specified termination action for each
Spot VM.
Spot VMs are excess Compute Engine capacity, so their
availability varies based on Compute Engine usage. You can help
mitigate availability issues for Spot VMs by following the best
practices, like viewing the availability of Spot VMs before creation,
as explained later in this document. Spot VMs don't have a minimum
or maximum runtime unless you specifically
limit the runtime.
If your workloads are fault-tolerant and can withstand possible VM
preemption, Spot VMs can reduce your Compute Engine
costs significantly. For example, batch processing jobs can run on
Spot VMs. If some of those VMs stop during processing, the
job slows but does not completely stop. Spot VMs complete your
batch processing tasks without placing additional load on your existing
VMs and without requiring you to pay full price for additional standard VMs.
Spot VMs limitations
Spot VMs function like standard VMs but have the
following limitations:
Compute Engine might preempt Spot VMs to reclaim
the resources at any time. Compute Engine preempts
Spot VMs for a variety of reasons—for example, system events.
The probability that Compute Engine preempts Spot VMs is
generally low, but might vary from day to day and from zone to zone depending
on current conditions. For more information, see
Preemption selection in this document.
Spot VMs are finite Compute Engine resources, so they
might not always be available.
Due to the preceding limitations, Spot VMs are not covered by any
Service Level Agreement and are excluded from the
Compute Engine SLA.
Preemption of Spot VMs
This section describes how Compute Engine preempts Spot VMs
and which VMs are selected for preemption. Additionally, instructions to detect,
handle, and test preemption of Spot VMs are explained later in
Manage preemption of Spot VMs.
Preemption process
Compute Engine performs the following steps to preempt
Spot VMs:
Compute Engine sends a preemption notice to the VM by updating
the preempted value in your VM's default metadata to TRUE, which your
workload can monitor to detect preemption.
The preemption notice duration
is the duration between this metadata signal and when
Compute Engine sends a
ACPI G2 Soft Off
signal to begin the shutdown period. The preemption notice duration affects
how your workload can handle preemption and can be set to one of the
following values while you are creating a Spot VM:
120 seconds:
We recommend setting the preemption notice duration to 120 seconds for any
workloads that need a dedicated duration or longer than 30 seconds to
handle preemption. You can handle preemption within your workload by
waiting for the VM to be preempted. (Optionally, you can also specify a
shutdown script, which runs during the following best-effort shutdown
period.)
0 seconds (default): If the preemption notice duration for a
Spot VM isn't specified or is set to 0, then there is no
dedicated delay between detecting preemption in metadata and the
ACPI G2 Soft Off signal. Your workload can handle the preemption notice
during the following shutdown period by using a shutdown script.
When the ACPI G2 Soft Off signal is sent, it
triggers any
shutdown script
that you have configured for the Spot VM and represents the
beginning of the shutdown period. The shutdown period for Spot VMs
is best effort and up to 30 seconds, which is shorter than the
shutdown period for other instances.
If the Spot VM hasn't stopped after the shutdown period,
Compute Engine sends an
ACPI G3 Mechanical Off
signal to the operating system.
The final state of Spot VMs varies
depending on your specified termination action for each VM:
If the termination action is set to STOP or not specified, then
Compute Engine stops the VM, transitioning the VM to a
TERMINATEDstate.
If the termination action is set to DELETE, then Compute Engine
deletes the VM.
If the preempted VM was stopped, it still appears in your project, but you are
not charged for the VM hours while it remains in a TERMINATED state. You can
access and recover data from any persistent disks that are attached to the VM,
but those disks still incur storage charges until you delete them.
As with standard VMs, persistent disks that are marked for auto-delete
are deleted when you delete Spot VMs.
If Compute Engine preempts Spot VMs less than one minute
after they are created, you are not billed for the use of those VMs. This
ensures that you don't pay for Spot VMs unless they have had time to
complete a significant amount of work. However, the charges for
premium operating systems are still calculated as
normal.
Preemption selection
Preemption can happen when Spot VMs are in a RUNNING state; while
in a TERMINATED state, Spot VMs are not considered for preemption.
As a result, you can reset the preemption process by
stopping
then restarting
Spot VMs, since stopping VMs leaves them in a TERMINATED state.
You can stop and restart preempted Spot VMs as many times as you
would like, as long as there is capacity. Notably,
resetting or rebooting VMs
instead leaves VMs in a RUNNING state and, thus, don't reset the preemption
process.
You can't view why any given preemption event occurred. Similar to
resource availability errors,
preemption rates can vary in different zones, at different times, or with
different resources. For specific suggestions on reducing your preemption rate,
see the
best practices.
Pricing
Spot prices, the prices for Spot VMs, provide significant discounts
for VMs. Spot prices give you discounts of up to 91% off of the on-demand price
for many machine types, GPUs, TPUs, and Local SSD disks.
Notably, if a preempted VM was stopped, you are not charged for the VM hours
while it remains in a TERMINATED state. You can access and recover data from
any persistent disks that are attached to the VM, but those disks still incur
storage charges until you delete them. Learn more about
instance uptime
and disk pricing.
This section provides notable information about using Spot VMs with
other Compute Engine offerings. Learn about using Spot VMs
with managed instance groups (MIGs), premium operating systems, local SSDs, and
GPUs. Additionally, understand how Spot VMs affect your quotas for
Compute Engine resources.
Spot VMs in a MIG
You can create Spot VMs in a
MIG by specifying the spot
provisioning model in an instance template
before you create or update the group.
MIGs can create or add new Spot VMs only when additional Compute Engine resources are available. If these resources are limited,
MIGs are unable to resize or automatically scale the number of Spot VMs in the group.
When using instance flexibility
that allows multiple machine types in the MIG, the MIG automatically selects
machine types with the lowest observed preemption rates to minimize workload
disruption.
MIGs always attempt to maintain their target size or the size specified by the
autoscaler for that group. If
Compute Engine stops one or more Spot VMs in a MIG, the
group repeatedly tries to recreate those VMs using the specified
instance template. If the necessary
resources become available again, the group recreates the VMs and maintains the
target group size.
Premium operating systems on Spot VMs
Spot VMs don't reduce the cost of
premium operating systems and
don't change the way that you're billed for the use of those operating systems.
If Compute Engine stops Spot VMs that run a premium
operating system, you are billed for that operating system as if you stopped
the VMs yourself. The charges for minimum usage still apply, and bills for
premium operating systems are still calculated by rounding up to the nearest
usage increment.
The machine types on Spot VMs that run premium operating systems
are always billed by the second, and follow the prices listed on the
Machine type pricing
page.
Local SSDs on Spot VMs
You can start Spot VMs with
local SSD disks and Compute Engine
charges you spot prices
for the local SSD disk usage. Local SSD disks attached to Spot VMs
work like normal local SSD disks, retain the same
data persistence characteristics,
and remain attached for the life of the VM.
Compute Engine doesn't charge you for local SSD disks if their VMs
are preempted in the first minute after they start running.
You can add GPUs to your Spot VMs
at lower spot prices for the GPUs. GPUs
attached to Spot VMs work like normal GPUs but persist only for
the life of the VM. Spot VMs with GPUs follow the same
preemption process
as all Spot VMs.
Consider requesting dedicated Preemptible GPU quota to use for GPUs on
Spot VMs. For more information, see
Quotas for Spot VMs.
During maintenance events, Spot VMs with GPUs are preempted by
default and cannot be automatically restarted. If you want to recreate your
VMs after they have been preempted, use a
managed instance group.
Managed instance groups recreate your VM instances if the vCPU, memory, and
GPU resources are available.
If you want a warning before your VMs are preempted, or want to
configure your VMs to automatically restart after a maintenance event, use
standard VMs with a GPU. For standard VMs with GPUs,
Compute Engine provides
one hour advance notice
before preemption.
Compute Engine does not
charge you for GPUs if their VMs are preempted in the first
minute after they start running.
Like other VMs, Spot VMs require available
CPU quotas. Additionally, if you plan
to use Spot VMs with local SSDs or with GPUs, Spot VMs
also require disk quota and
GPU quota respectively.
If you use Spot VMs with these resources and have not requested
preemptible quota, Spot VMs consume your standard quota for these
resources. If you plan to use Spot VMs, consider requesting
preemptible quota for those resources to prevent Spot VMs from
consuming your other quotas.
After Compute Engine grants you preemptible quota in a region, all
Spot VMs (and any preemptible VMs)
in that region count against that quota. All standard VMs in that region
continue to count against the standard quota. In regions where you don't have
preemptible quota, you can use standard quota to launch Spot VMs.
Preemptible quota is not visible in the gcloud CLI or
Google Cloud console quota pages unless Compute Engine has granted
the quota. For more information, see
Allocation quotas for preemptible resources.
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.
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