Viewing and applying idle resources recommendations

Compute Engine provides recommendations to help you identify resources like persistent disks (PDs), IP addresses, and custom disk images that aren't used. You can use idle resource recommendations to help minimize waste of resources and reduce your compute bill. For PDs that are not actively used, you can create a backup snapshot then delete the resource. For unused PDs, images, and IP addresses, you can delete them if you don't need them.

If you're interested in idle VM recommendations, see Viewing and applying idle VM recommendations.

Before you begin

If you want to use the command-line examples in this guide, do the following:
1. Install or update to the latest version of the Google Cloud CLI.
2. Set a default region and zone.
If you want to use the API examples in this guide, set up API access.

Pricing

Idle resources recommendations are available free of charge.

Recommendation generation

If a resource has not been attached to a VM or other resource for 15 days, the Recommender classifies that resource as idle.

One of the following conditions must be met in order to classify a resource as idle and generate the corresponding recommended action:

Resource	Condition for resource to be classified as idle	Recommended action	Savings
PD	Created at least 15 days ago AND Never attached to a VM AND Is blank	Delete	Save 100% of the cost of that disk (see disk pricing)
PD	Detached for at least 15 days	Create snapshot and delete	Reduce the maintenance cost of that disk by 35% to 92% (see disk pricing)
Custom image	Not used to create a disk for at least 15 days AND Not used in any instance template	Delete	Save 100% of the cost of that image (see image pricing)
IP address	Not attached to any resource for at least 15 days	Delete	Save 100% of the cost of that IP address (see IP pricing)

Recommendation frequency

Idle resource recommendations begin 15 days after resource creation, and they are updated once every 24 hours.

Viewing recommendations

To view recommendations about idle resources, use the gcloud CLI or the API.

Permissions required for this task

To perform this task, you must have the following permissions:

recommender.computeDiskIdleResourceRecommendations.list on the project for idle PDs
recommender.computeAddressIdleResourceRecommendations.list on the project for idle IPs
recommender.computeImageIdleResourceRecommendations.list on the project for idle custom images

Console

In the Google Cloud console, go to the Recommendations page.

Go to Recommendations

All idle resources are listed under Unused Compute Engine resources.

gcloud

Use the gcloud recommender recommendations list command with the --recommender=RECOMMENDER_ID flag:

gcloud recommender recommendations list \
    --project=PROJECT_ID \
    --location=LOCATION \
    --recommender=RECOMMENDER_ID \
    --format=yaml

Replace the following:

PROJECT_ID: the ID of your project.
LOCATION: the location that contains the resources for which you want recommendations.
- For PDs specify a zone or region, for example, us-central1-c.
- For IPs:
  - To list regional IPs, you must specify a region.
  - To list global IPs, specify global. For more information about regional and global IP address resources, see IP addresses.
- For custom images specify global.
RECOMMENDER_ID: the id of recommender
- For disks, specify google.compute.disk.IdleResourceRecommender.
- For images, specify google.compute.image.IdleResourceRecommender.
- For IPs, specify google.compute.address.IdleResourceRecommender.

For example, the following command lists idle PD recommendations in us-central1-c for test-project:

gcloud recommender recommendations list \
    --project=test-project \
    --location=us-central1-c \
    --recommender=google.compute.disk.IdleResourceRecommender \
    --format=yaml


---
content:
    operationGroups:
    - operations:
      - action: add
        resource: //compute.googleapis.com/projects/test-project/global/snapshots/$snapshot-name
        resourceType: compute.googleapis.com/Disk
        path: /
        value:
        - name: $snapshot-name
          sourceDisk: projects/test-project/locations/us-central1-c/disks/pd-name
          storageLocations: us-central1
      - action: remove
        resource: //compute.googleapis.com/projects/test-project/zones/us-central1-c/disks/pd-name
        resourceType: compute.googleapis.com/Disk
        path: /
description: Save cost by snapshotting and then deleting idle persistent disk 'pd-name'
name: projects/test-project/locations/us-central1-c/recommenders/google.compute.disk.IdleResourceRecommender/recommendations/0fd31b24-cc05-4132-8431-ed54a22dd4f1
recommenderSubtype: SNAPSHOT_AND_DELETE_DISK
lastRefreshTime:
  seconds: 1543912652
primaryImpact:
  category: COST
  costProjection:
    cost:
      currencyCode: USD
      units: '-50'
    duration:
      seconds: 2592000
stateInfo: ACTIVE
etag: "cb0e6ac2cfc0b591"

Learn more about using gcloud CLI to work with recommendations.

API

Call the recommendations.list method and specify the recommender id, for example google.compute.disk.IdleResourceRecommender:

GET https://recommender.googleapis.com/v1/projects/PROJECT_ID/locations/LOCATION/recommenders/RECOMMENDER_ID/recommendations

Replace the following:

PROJECT_ID: the ID of your project.
LOCATION: the location that contains the resources for which you want recommendations.
- For PDs specify a zone or region, for example, us-central1-c.
- For IPs:
  - To list regional IPs, you must specify a region.
  - To list global IPs, specify global. For more information about regional and global IP address resources, see IP addresses.
- For custom images specify global.
RECOMMENDER_ID: the id of recommender
- For disks, specify google.compute.disk.IdleResourceRecommender.
- For images, specify google.compute.image.IdleResourceRecommender.
- For IPs, specify google.compute.address.IdleResourceRecommender.

The following example bash script uses an access token returned by Application Default Credentials, for a curl request. For information about about setting up Application Default Credentials, see Provide credentials for Application Default Credentials.

PROJECT_ID=test-project
LOCATION=us-central1-c
RECOMMENDER_ID=google.compute.disk.IdleResourceRecommender

curl -H "Authorization: Bearer $(gcloud auth application-default print-access-token)" \
  https://recommender.googleapis.com/v1/projects/$PROJECT_ID/locations/$LOCATION/recommenders/$RECOMMENDER_ID/recommendations

Example JSON response for idle PD recommendation:

{
 "description" : "Save cost by deleting idle persistent disk 'pd-name'",
 "name": "projects/test-project/locations/us-central1-c/recommenders/"
         "google.compute.disk.IdleResourceRecommender/"
         "recommendations/0fd31b24-cc05-4132-8431-ed54a22dd4f1",
 "recommenderSubtype" : "SNAPSHOT_AND_DELETE_DISK",
 "lastRefreshTime": {
   "seconds": 1543912652
 },
 "primaryImpact": {
   "category": COST,
   "costProjection": {
    "cost": {"currencyCode": "USD", "units": -50},
    "duration": { "seconds": 2592000 }
   }
 },
 "stateInfo": ACTIVE,
 "content": {
   "operationGroups" : [
    {
      "operations" : [
       {
         "action": "add",
         "resourceType": "compute.googleapis.com/Disk",
         "resource" : "//compute.googleapis.com/projects/test-project/global/snapshots/$snapshot-name",
         "value": {
           "name": "$snapshot-name",
           "sourceDisk": "projects/test-project/zones/us-central1-c/disks/pd-name",
           "storageLocations": ["us-central1"],
         }
       },
       {
         "action": "remove",
         "resourceType": "compute.googleapis/Disk",
         "resource": "//compute.googleapis.com/projects/test-project/"
                     "zones/us-central1-c/disks/pd-name"
       }
      ]
    }
   ]
 },
 "associatedInsights": [
    {
      "insight": "projects/test-project/locations/us-central1-c/insightTypes/google.compute.disk.IdleResourceInsight/insights/31326443-bcc3-4776-9b86-48879fddb656"
    }
  ],
 "etag": "cb0e6ac2cfc0b591"
}

Interpreting the recommendation response

Each recommendation that you receive through the gcloud CLI or API contains operation groups, with operations that you can perform in serial to apply the recommendation. For example, idle PD recommendation operation groups include one or two operations:

If your idle PD has data on it, the recommendation includes an add operation to create a snapshot to back up the PD. For example:

   {
     "action": "add",
     "resourceType": "compute.googleapis.com/Disk",
     "resource" : "//compute.googleapis.com/projects/test-project/global/snapshots/$snapshot-name",
     "path": "/",
     "value": {
       "name": "$snapshot-name",
       "sourceDisk": "projects/test-project/zones/us-central1-c/disks/pd-name",
       "storageLocations": ["us-central1"]
     }
   }

A remove operation to permanently delete the idle PD. For example:

   {
     "action": "remove",
     "resourceType": "compute.googleapis.com/Disk",
     "resource" : "//compute.googleapis.com/projects/test-project/zones/us-central1-c/disks/pd-name",
     "path": "/"
   }

See Applying idle PD recommendations to create a snapshot of and to delete a PD, deleting idle IPs to remove unused IP addresses, and deleting idle custom images to remove unused custom disk images.

Viewing insights for idle resource recommendations

The Recommender generates recommendations based on resource insights. By viewing insights on resources you can learn more about those resources, such as how long a resource has been detached from a VM or whether a PD is blank.

If you want to view the insight that generated the recommendation, you can use the gcloud CLI or API.

Permissions required for this task

To perform this task, you must have the following permissions:

recommender.computeDiskIdleResourceInsights.list on the project for idle PDs
recommender.computeAddressIdleResourceInsights.list on the project for idle IPs
recommender.computeImageIdleResourceInsights.list on the project for idle images

gcloud

Use the insights list command

gcloud beta recommender insights list --project=PROJECT_NAME \
  --location=LOCATION --insight-type=INSIGHT_TYPE

Replace the following:

LOCATION: the location that contains the resources for which you want insights.
- For PDs specify a zone or region, for example, us-central1-c.
- For IPs:
  - To list regional IPs, you must specify a region.
  - To list global IPs, specify global. For more information about regional and global IP address resources, see IP addresses.
- For custom images specify global.
INSIGHT_TYPE: the id of the insight type
- For disks, specify google.compute.disk.IdleResourceInsight.
- For images, specify google.compute.image.IdleResourceInsight.
- For IPs, specify google.compute.address.IdleResourceInsight.

API

Use the insights.list method.

GET https://recommender.googleapis.com/v1beta1/projects/PROJECT_ID/locations/LOCATION/insightTypes/INSIGHT_TYPE/insights

Replace the following:

PROJECT_ID: the ID of your project.
LOCATION: the location that contains the resources for which you want insights.
- For PDs specify a zone or region, for example, us-central1-c.
- For IPs:
  - To list regional IPs, you must specify a region.
  - To list global IPs, specify global. For more information about regional and global IP address resources, see IP addresses.
- For custom images specify global.
INSIGHT_TYPE: the id of the insight type
- For disks, specify google.compute.disk.IdleResourceInsight.
- For images, specify google.compute.image.IdleResourceInsight.
- For IPs, specify google.compute.address.IdleResourceInsight.

Here is an example response of an insight on an idle PD resource:

{
  "name": "projects/test-project/locations/us-central1-c/insightTypes/google.compute.disk.IdleResourceInsight/insights/0ec21a13-bb04-3121-7321-dc43a11cc3e2",
  "description": "Disk 'pd-name' in zone 'us-central1-c' was last used 17 days ago. Consider taking snapshot and delete it.",
  "targetResources": [
    "//compute.googleapis.com/projects/test-project/zones/us-central1-c/disks/pd-name"
  ],
  "insightSubtype": "IDLE_DISK",
  "content": {
    "diskLastUseTime": "2019-10-01 13:00:00",
    "isBlank": false,
  },
  "lastRefreshTime": "2019-10-10 13:00:00",
  "observationPeriod": "15 days",
  "stateInfo": {
    "state": "ACTIVE"
  },
  "category": "COST",
  "etag": "fds421j2349",
  "associatedRecommendations": [
    {
      "projects/test-project/locations/us-central1-c/recommenders/"
      "google.compute.disk.IdleResourceRecommender/"
      "recommendations/0fd31b24-cc05-4132-8431-ed54a22dd4f1"
    }
  ]
}

The example response includes the following fields:

diskLastUseTime: The last time when the disk was attached to a VM. If the disk was never attached to a VM this is set to the disk's creation time.
isBlank: This field is set to true if disk is blank and was never attached to VM. Otherwise it is false.

For more information about insights, see the reference docs.

Applying idle resource recommendations

If you receive a recommendation about an idle resource and you decide that you want to follow the recommendation, follow the instructions below.

Deleting idle IP address

See the addresses.delete method, gcloud compute addresses delete command, or the Releasing a static external IP address documentation.

Deleting idle custom images

See the images.delete method, gcloud compute images delete command, or the Deleting an image documentation.

Applying idle PD recommendations

If you need to create a snapshot of a PD prior to deleting it, see Creating persistent disk snapshots.

To delete an idle PD, see the gcloud compute disks delete command.

For information about how to recover data from a snapshot and recreate your PD, see Restoring snapshots.