This document gives an overview of resize requests in a managed instance group(MIG). To learn more about other ways to add virtual machine (VM) instances to aMIG, seeAdd instances to a MIG.

Use MIG resize requests for the following benefits:

• Create VMs in the MIG all at once. When resources are available, the MIGcreates VMs all at once. This approach helps you avoid charges for partialcapacity until all resources become available.

• Obtain high-demand resources. You can use MIG resize requests with theflex-start or reservation-bound provisioning models. These provisioningmodels give you the following benefits:

  • You have higher chances of obtaining high-demand resources like GPUs.

  • Based on the machine type that your requested VMs use, you get adiscount up to 53% for memory, vCPUs, and any attached GPUs.

Use cases

You can use resize requests in a MIG for the following:

• Create Flex-start VMs. You can request to createFlex-start VMs forobtaining resources as soon as they are available. These VMs are suitablefor workloads that need to run for up to seven days, but can start at anytime. When you use resize requests to create Flex-start VMs,the following occurs:

  • The MIG schedules Flex-start VM creation as soon asresources are available.

  • After the MIG creates the requested Flex-start VMs, theVMs run until one of the following occurs:

    • Compute Engine deletes the Flex-start VMs atthe end of their run duration.

    • You delete the Flex-start VMs.

• Create VMs by consuming a reservation. You can request to createVMs that use the reservation-bound provisioning modelto consume a reservation. When you use resize requests to consume areservation, the following occurs:

  • The MIG creates VMs at or after the reservation start time.

  • After the MIG creates the requested VMs, the VMs run until one of thefollowing occurs:

    • Compute Engine deletes the reservation at its end time.

    • You stop or delete the VMs.

How resize requests work

The following sections explain how MIG resize requests work.

On creation

To create a MIG resize request, specify the following properties:

• To define the number of VMs to create, use one of the following properties:

  • resizeBy: the number of VMs to create. The MIG automaticallygenerates VM names.

  • instanceNames: a list of VM names. The MIG creates one VM for eachname that you specify. This property is inPreview. Useit if your workload requires specific VM names.

• requestedRunDuration: how long the VMs must run for. The run durationmust be between 10 minutes and seven days. This property is optional. If youuse MIG resize requests to create VMs as soon as resources are available,then this property overrides the run duration that is specified in the MIG'sinstance template.

After creation

After you create a MIG resize request, the request goes through differentstates. The following diagram shows these states:

The states shown in the preceding diagram are as follows:

• CREATING: Compute Engine received the resize request, theMIG's target size increases by the number of VMs that are specified in therequest, and the MIG creates managed instances that are in aCREATINGstate. These managed instances represent the VMs that the MIG creates whenthe resize request succeeds.

• ACCEPTED: Compute Engine created and accepted the request.Based on youruse case for MIG resize requests,Compute Engine does one of the following:

  • Create Flex-start VMs. On a best-effort basis, theDynamic Workload Schedulerschedules Flex-start VM creation based on availability andthe run duration that is specified in the request. If you lackstandard or preemptible allocation quota,or if resources are temporarily unavailable, then the Dynamic Workload Schedulermaintains the request until you have sufficient quota and resourcesbecome available.

    Note: Even though a MIG creates Flex-start VMs for aresize request only when all the requested capacity is available, inrare cases, the MIG might create only some of the requested number ofVMs but fail to create the remaining ones. If this failure occurs, thenthe MIG automatically deletes these VMs as soon as possible to minimizeunwanted charges. The state of the request remainsACCEPTED and theMIG retries creating the VMs all at once.

  • Create VMs by consuming a reservation. If the auto-createdreservation that you're targeting for consumption has reached its starttime, then the request transitions toSUCCEEDED. Otherwise, therequest persists until the reservation reaches its start time.

• SUCCEEDED: the MIG created the requested number of VMs all at once.Based on your use case for MIG resize requests, the following occurs:

  • When the MIG creates VMs as soon as resources are available, the VMs rununtil the MIG deletes them at the end of their run duration, or untilyou delete the VMs. You can't recreate, stop, or suspend the VMs.

  • When the MIG creates VMs by consuming an auto-created reservation, theVMs run until the reservation period ends, or until you stop, suspend,or delete the VMs.

• FAILED: the resize request failed due to a technical error. As aresult, Compute Engine decreases the target size of the MIG by thenumber of requested VMs.

• CANCELLED: a usercanceled the resize request.When you cancel a resize request, Compute Engine stops the MIG fromcreating the requested resources. After you cancel a resize request,Compute Engine decreases the MIG's target size by the number ofrequested VMs and deletes the request after 14 days. Optionally, you candelete the resize requestbefore Compute Engine deletes it.

If you delete a MIG that contains resize requests, then this deletion alsoremoves any resize requests and VMs in the MIG. However, if you delete a MIGwhen the MIG creates VMs to fulfill a resize request, Compute Enginewaits until the MIG has finished creating the requested number of VMs and thestate of the resize request transitions toSUCCEEDED before deleting the MIG.

Quota

Based on youruse case for MIG resize requests, you need quota asfollows:

• Create Flex-start VMs. Quota requirements vary based onthe machine type that your requested number of Flex-start VMsuse. If you lack quota for your requested resources, then a resize requestremains pending until you have sufficient quota. For more information aboutquotas that apply to Compute Engine resources, seeAllocation quotas.

• Create VMs by consuming a reservation. You don't need quota in this usecase. This requirement is because you use thereservation-bound provisioning modelto consume an auto-created reservation for a future reservation in calendarmode.

Pricing

You don't incur charges when you create, cancel, or delete resize requests in aMIG. Instead, based on youruse case for MIG resize requests, youincur charges as follows:

• If you use MIG resize Flex-start VMs, then you incur chargesas follows:

  • Charges begin when the MIG creates the Flex-start VMs.Google Cloud charges you for the Flex-start VMs based onDynamic Workload Scheduler pricing.

  • Charges end when the MIG deletes the Flex-start VMs atthe end of their run duration, or when you delete theFlex-start VMs.

  Important: If a MIG creates only some requestedFlex-start VMs and fails to create the rest, then you mightstill incur charges for any created Flex-start VMs. Thesecharges apply until the MIG automatically deletes theFlex-start VMs.

• If you use MIG resize requests to create VMs by consuming a reservation,then you incur charges as follows:

  • When the MIG creates the VMs, you don't incur charges again for theconsumed reservation resources. You only incur charges for resourcesthat the VMs use and that aren't part of the reservation, such as disksor IP addresses.

  • Charges end at the reservation end time. At this time,Compute Engine deletes the reservation and any VMs that consumeit. For more information, see thebilling for reservations.

Limitations

The following sections explain the limitations for MIG resize requests.

Limitations for resize requests

MIG resize requests have the following limitations:

• You can use MIG resize requests to obtain different machine types dependingon the provisioning model that you use:

  • Flex-start: you can obtain any GPU machine type (except A4X and G4),and H4D machine types. Use this model to createFlex-start VMs as soon as resources are available.

  • Reservation-bound: you can only obtain A4, A3 Ultra, or H4D machinetypes. Use this model to create VMs by consuming a reservation.

• You can only cancel resize requests that are in theACCEPTED state.

• You can only delete a resize request after it succeeds (SUCCEEDED), fails(FAILED), or is canceled (CANCELLED).

Limitations for the instance template

For the MIG's instance template, the following limitations apply:

• You must specify to stop VMs duringhost maintenance events.

• You can't specifyplacement policies.

• Based on youruse case for MIG resize requests, you mustspecify the following configurations when you create the instance template:

  • To create Flex-start VMs, you must specify the following:

    • To delete VMs at the end of their run duration by using themaxRunDuration andinstanceTerminationAction fields.

    • Toprevent reservations consumption.

    • To use theflex-start provisioning model.

  • To create VMs by consuming an auto-created reservation for a futurereservation in calendar mode, you must specify the following:

    • To delete VMs at the end of the reservation period by using theinstanceTerminationAction field.

    • Totarget the reservation for consumption.

    • To use thereservation-bound provisioning model.

Limitations for the MIG

For the MIG, the following limitations apply:

• In a regional MIG, you can only use theANY_SINGLE_ZONE target distribution shape.

• You mustturn off repairsin the MIG.

• You mustdelete the autoscaling configuration.

• You can't apply VM configuration updates to the VMs created through resizerequests. To prevent automatic updates,set the MIG's update type to opportunistic.

• You can't apply theall-instances configuration toVMs created through resize requests.

• You can't defineper-instance configurationsin VMs created through resize requests.

• You can only set thestandby pool modeof the MIG tomanual (default).

• If a MIG contains accepted resize requests, then you can't do the following:

  • You can't add a second instance template to initiate acanary update in the MIG.

  • You can't change thetarget size of the MIG.

• You can't delete or abandon the managed instances in aCREATING statusthat the MIG creates for a resize request. To delete those managedinstances, you mustcancel the resize request.

• If you use MIG resize requests to create Flex-start VMs, thenyou can'tstop orrecreate VMs.

What's next

• Learn how tocreate resize requests in a MIG.

• Learn how toview, cancel, or delete resize requests in a MIG.