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Adding disk, memory, and CPU

Adding disk, memory, and CPU

For new hosting models, scaling is available through the CLI, API, and Terraform.

To scale an Isolated compute host flavor instance, set the relevant hostflavor parameter to the Isolated Compute size you're targeting, such as "b3c.4x16.encrypted". As this includes CPU and RAM allocation selections, do not separately select CPU and RAM.

To scale a Shared compute host flavor instance between the minimum CPU value and 2 CPU, set the CPU to 0 and scale the RAM allocation using the following commands. The CPU value will scale as a ratio of 1 CPU : 8 GB RAM, up to 2 CPU. To scale above 2 CPU, set the CPU and RAM allocations to your target allocation. For both, make sure to include the relevant hostflavor parameter.

To scale an Isolated compute host flavor instance, set the relevant host_flavor parameter to the Isolated Compute size you're targeting, such as "b3c.4x16.encrypted". As this includes CPU and RAM allocation selections, do not separately select CPU and RAM.

To scale a Shared compute host flavor instance between the minimum CPU value and 2 CPU, set the CPU to 0 and scale the RAM allocation using the following commands. The CPU value will scale as a ratio of 1 CPU : 8 GB RAM, up to 2 CPU. To scale above 2 CPU, set the CPU and RAM allocations to your target allocation. For both, make sure to include the relevant host_flavor parameter.

To scale an Isolated compute host flavor instance, set the relevant host_flavor parameter to the Isolated Compute size you're targeting, such as "b3c.4x16.encrypted". As this includes CPU and RAM allocation selections, do not separately select CPU and RAM.

To scale a Shared compute host flavor instance between the minimum CPU value and 2 CPU, set the CPU to 0 and scale the RAM allocation using the following commands. The CPU value will scale as a ratio of 1 CPU : 8 GB RAM, up to 2 CPU. To scale above 2 CPU, set the CPU and RAM allocations to your target allocation. For both, make sure to include the relevant host_flavor parameter.

You can manually adjust the resources available to your IBM Cloud® Databases for PostgreSQL deployment to suit your workload and the size of your data.

Resource breakdown

Databases for PostgreSQL deployments have two data members in a cluster, and resources are allocated to both members equally. For example, the minimum storage of a PostgreSQL deployment is 10240 MB, which equates to an initial size of 5120 MB per member. The minimum RAM for a PostgreSQL deployment is 8192 MB, which equates to an initial allocation of 4096 MB per member.

Billing is based on the total resources that are allocated to the service.

Disk usage

Storage shows the amount of disk space that is allocated to your service. Each member gets an equal share of the allocated space. Your data is replicated across all the data members in the PostgreSQL database cluster.

Disk allocation also affects the performance of the disk, with larger disks having higher performance. Baseline input/output operations per second (IOPS) performance for disk is 10 IOPS for each GB. Scale disk to increase the IOPS that your deployment can handle.

You cannot scale down storage. If your data set size has decreased, you can recover space by backing up and restoring to a new deployment.

RAM

If you find that your queries and database activity suffer from performance issues due to a lack of memory, you can scale the amount of RAM allocated to your service. If your database instance is on an Isolated Compute hosting model, select the CPU x RAM configuration that matches your resource needs. If your database instance is on a Shared Compute or Dedicated Core hosting model, select the RAM allocation that you want for your database.

Dedicated Core is deprecated, and will be removed in May 2025.

Adding memory to the total allocation adds memory to the members equally. Databases for PostgreSQL deployments have their memory allocation policy set at 50% heap and 50% system memory, so increasing the amount of RAM increases both heap and system memory. RAM can be scaled up or down.

work_mem, maintenance_work_mem, and effective_cache_size are auto-tuned based on the deployment's total memory. They are also set when you scale memory on your deployment. When you scale, the values are adjusted without outage to the running deployment.

The amount of memory allocated to the database's shared buffer pool is not adjusted automatically when you scale your deployment. Setting it to 25% of the deployment's total memory is recommended. You can manually tune the shared buffer pool through the shared_buffer setting in your PostgreSQL's configuration. It is not auto-tuned because changing the shared_buffer requires a database restart.

vCPU

If you find that your database workloads need more CPU resources, you can scale the amount of CPU allocated to your service. If your database instance is on an Isolated Compute hosting model, select the CPU x RAM configuration that matches your resource needs. If your database instance is on a Shared Compute or Dedicated Core hosting model, select the CPU allocation that you want for your database.

Old style dedicated core instances are deprecated, and will be removed in May 2025. Learn more about the new hosting models here.

Scaling considerations

  • Scaling up might cause your deployment to restart. If your deployment needs to be moved to a host with more capacity, the deployment is restarted as part of the move.
  • Scaling down RAM or CPU does not trigger restarts.
  • Disk cannot be scaled down.
  • Scaling between hosting models (Shared Compute, Isolated Compute, and Dedicated Cores) moves your deployment to new hosts. Your databases are restarted as part of that move. As your deployment is moved to a new host, this can also take longer than just adding more resources. For more information, see Shared compute and Isolated compute.
  • Similarly, drastically scaling up CPU, RAM, or disk can take longer to run than small resource increases to account for provisioning more underlying hardware resources.
  • Scaling operations are logged in IBM Cloud® Activity Tracker.
  • If you find consistent trends in resource usage or want to scale when certain resource thresholds are reached, enable autoscaling on your deployment.
  • Databases for PostgreSQL is designed to balance work load across a cluster and can benefit from being horizontally scaled. If you are concerned about performance, check out Adding PostgreSQL members.

Scaling in the UI

For new hosting models, scaling is currently available through the CLI, API, and Terraform.

A visual representation of your data members and their resource allocation is available on the Resources tab from the left-hand navigation panel.

The scale resources panel in Resources
The Scale Resources Panel

Adjust the slider to increase or decrease the resources that are allocated to your service. The slider controls how much memory or disk is allocated per member. The UI currently uses a coarser-grained resolution of 8 GB increments for disk and 1 GB increments for memory. The UI shows the total allocated memory or disk for the position of the slider. Click Scale to trigger the scaling operations and return to the dashboard overview.

Review current resources and hosting model

IBM Cloud CLI cloud databases plug-in supports viewing and scaling the resources on your deployment. Use the command cdb deployment-groups to see current resource information for your service, including which resource groups are adjustable. To scale any of the available resource groups, use cdb deployment-groups-set command.

For example, with the following command you can view the resource groups for a deployment named "example-deployment". Note that this command will also reveal if your database is a Shared Compute or Isolated Compute instance through the hostflavor attribute. If the hostflavor is null, it is on an old style hosting model.

ibmcloud cdb deployment-groups example-deployment

This produces the output:

Group   member
Count   2
|
+   Memory
|   Allocation              8192mb
|   Allocation per member   4096mb
|   Minimum                 4096mb
|   Step Size               256mb
|   Adjustable              true
|
+   CPU
|   Allocation              6
|   Allocation per member   3
|   Minimum                 6
|   Step Size               2
|   Adjustable              true
|
+   Disk
|   Allocation              10240mb
|   Allocation per member   5120mb
|   Minimum                 10240mb
|   Step Size               1024mb
|   Adjustable              true

The deployment has two members, with 4096 MB of RAM and 10240 MB of disk allocated in total. The "per member" allocation is 4096 MB of RAM and 5120 MB of disk. The minimum value is the lowest the total allocation can be set. The step size is the smallest amount by which the total allocation can be adjusted.

Resources and scaling in the CLI

The cdb deployment-groups-set command allows either the total RAM or total disk allocation to be set in MB. For example, to scale the memory of the "example-deployment" to 4096 MB of RAM for each memory member (for a total memory of 8192 MB), you use the command:

ibmcloud cdb deployment-groups-set example-deployment member --memory 8192

Determine the hosting model of your database

Use the following command to review the value of the host_flavor attribute. This will be null if the database is on a deprecated hosting model (not Shared or Isolated Compute).

ibmcloud cdb groups <INSTANCE_NAME_OR_CRN> --json

Switching to and between Hosting Models in the CLI

If your database is a Shared compute instance, you can adjust the memory, CPU, and disk options with the following command. This can also be used to move a database from a different hosting model to the Shared Compute hosting model.

ibmcloud cdb deployment-groups-set <INSTANCE_NAME_OR_CRN> <GROUP_ID> [--memory <val>] [--cpu <val>] [--disk <val>] [--hostflavor multitenant]

For example, use the following to scale to a Shared Compute instance or scale up your Shared Compute instance:

ibmcloud cdb deployment-groups-set crn:abc ... xyz:: member  --memory 24576 --cpu 6  --hostflavor multitenant

If your database is an Isolated compute instance, memory and CPU are adjusted together by selecting the Isolated Compute size (see all sizes in Table 1). Disk is scaled separately. To scale a Cloud Databases Isolated Compute instance, use a command, such as the following that is used to scale to a 4 CPU by 16 RAM instance. This command can also be used to move a database from a different hosting model to the Isolated Compute hosting model.

Note that since the host flavor selection includes CPU and RAM sizes (b3c.4x16.encrypted is 4 CPU and 16 RAM), this request does not accept both an Isolated size selection and separate CPU and RAM allocation selections.

ibmcloud cdb deployment-groups-set <INSTANCE_NAME_OR_CRN> <GROUP_ID> [--disk <val>] [--hostflavor <hostflavor>]

For example, use the following to scale to an Isolated Compute instance or scale up your Isolated Compute instance:

ibmcloud cdb deployment-groups-set crn:abc ... xyz:: member  --hostflavor b3c.4x16.encrypted

The hostflavor parameter

The hostflavor parameter defines your compute sizing. To provision a Shared Compute instance, specify multitenant. To provision an Isolated Compute instance, input the appropriate value for your desired CPU and RAM configuration.

Host flavor sizing parameter
Host flavor hostflavor value
Shared Compute multitenant
4 CPU x 16 RAM b3c.4x16.encrypted
8 CPU x 32 RAM b3c.8x32.encrypted
8 CPU x 64 RAM m3c.8x64.encrypted
16 CPU x 64 RAM b3c.16x64.encrypted
32 CPU x 128 RAM b3c.32x128.encrypted
30 CPU x 240 RAM m3c.30x240.encrypted

Review current resources and hosting model

The Foundation Endpoint that is shown on the Overview panel of your service provides the base URL to access this deployment through the API. Use it with the /groups endpoint if you need to manage or automate scaling programmatically.

To view the current and scalable resources on a deployment, use the /deployments/{id}/groups endpoint. Note that this command will also reveal if your database is a Shared Compute or Isolated Compute instance through the host_flavor attribute. If the host_flavor is null, it is on an old style hosting model.

curl -X GET -H "Authorization: Bearer $APIKEY" 'https://api.{region}.databases.cloud.ibm.com/v5/ibm/deployments/{id}/groups'

Scaling with the API

To scale the memory of a deployment to 4096 MB of RAM for each member (there are 2 so a total memory of 8192 MB), use the /deployments/{id}/groups/{group_id} API endpoint.

curl -X PATCH 'https://api.{region}.databases.cloud.ibm.com/v5/ibm/deployments/{id}/groups/member' \
-H "Authorization: Bearer $APIKEY" \
-H "Content-Type: application/json" \
-d '{"memory": {
        "allocation_mb": 8192
      }
    }'

Determine the hosting model of your database

Use the following command to review the value of the host_flavor attribute. This will be null if the database is on a deprecated hosting model (not Shared or Isolated Compute).

curl -X GET https://api.{region}.databases.cloud.ibm.com/v5/ibm/deployments/{id}/groups -H 'Authorization: Bearer <>' \

Switching to and between Hosting Models in the API

To scale any Cloud Databases Shared Compute instance, use the the following command, setting host_flavor to multitenant. If your database is not on Shared Compute, this command will also move a database from a different hosting model to the Shared Compute hosting model.

curl -X PATCH https://api.{region}.databases.cloud.ibm.com/v5/ibm/deployments/{id}/groups/member
-H 'Authorization: Bearer <>'
-H 'Content-Type: application/json'
-d '{"host_flavor":
        {"id": "multitenant"},
      "cpu":
        {"allocation_count": 2},
      "memory":
        {"allocation_mb": 8192}
    }' \

To scale any instance into a Cloud Databases Isolated Compute instance or to scale to a different Isolated Compute size, use the host_flavor parameter, this time set to the desired Isolated Compute size. Available hosting sizes and their host_flavor value parameters are listed in Table 1. For example, {"host_flavor": "b3c.4x16.encrypted"}. Note that since the host flavor selection includes CPU and RAM sizes (b3c.4x16.encrypted is 4 CPU and 16 RAM), this request does not accept both, an Isolated size selection and separate CPU and RAM allocation selections. Scale with the Cloud Databases API Scaling endpoint, with a command like:

curl -X PATCH https://api.{region}.databases.cloud.ibm.com/v5/ibm/deployments/{id}/groups/member
-H 'Authorization: Bearer <>'
-H 'Content-Type: application/json'
-d '{"host_flavor": {"id": "b3c.4x16.encrypted"}}' \

CPU and RAM allocation is not allowed when provisioning or scaling through Isolated Compute. Specify mulitenant for the host_flavor parameter to have independent CPU and RAM selections.

CPU and RAM autoscaling is not supported on Cloud Databases Isolated Compute. Disk autoscaling is available. If you have provisioned an Isolated instance or switched over from a deployment with autoscaling, keep an eye on your resources using IBM Cloud® Monitoring integration, which provides metrics for memory, disk space, and disk I/O utilization. To add resources to your instance, manually scale your deployment.

The host flavor parameter

{: api

The host_flavor parameter defines your compute sizing. To provision a Shared Compute instance, specify multitenant. To provision an Isolated Compute instance, input the appropriate value for your desired CPU and RAM configuration.

Table 1 Host flavor sizing parameter
Host flavor host_flavor value
Shared Compute multitenant
4 CPU x 16 RAM b3c.4x16.encrypted
8 CPU x 32 RAM b3c.8x32.encrypted
8 CPU x 64 RAM m3c.8x64.encrypted
16 CPU x 64 RAM b3c.16x64.encrypted
32 CPU x 128 RAM b3c.32x128.encrypted
30 CPU x 240 RAM m3c.30x240.encrypted

Review current resources and hosting model

Review resource allocations to your database by checking your terraform scripts for cpu { allocation_count = }, memory {allocation_mb = }, and disk { allocation_mb = }. Review the host_flavor setting to determine if your database is a Shared Compute or Isolated Compute style hosting model. If host_flavor does not exist, your database is on an old style hosting model.

Scaling with Terraform

Before executing a Terraform script on an existing instance, use the terraform plan command to compare the current infrastructure state with the desired state defined in your Terraform files. Any alteration to the resource_group_id, service plan, version, key_protect_instance, key_protect_key, backup_encryption_key_crn attributes recreates your instance. For a list of current argument references with the Forces new resource specification, see the ibm_database Terraform Registry.

Scale your instance by adjusting your Terraform script for the resource you're interested in. In the following example, cpu, memory, and disk allocations are specified. Note that if you have a host flavor selected (Isolated Compute or Shared Compute Multitenant), keep the host flavor selection in your script. To implement your change, run terraform apply.

data "ibm_resource_group" "group" {
  name = "<your_group>"
}
resource "ibm_database" "<your_database>" {
  name              = "<your_database_name>"
  plan              = "standard"
  location          = "eu-gb"
  service           = "databases-for-epostgresql"
  resource_group_id = data.ibm_resource_group.group.id
  tags              = ["tag1", "tag2"]
  adminpassword     = "password12"
  group {
    group_id = "member"
    cpu {
      allocation_count = 6
    }
    memory {
      allocation_mb = 24576
    }
    disk {
      allocation_mb = 256000
    }
  }
  users {
    name     = "user123"
    password = "password12"
  }
  allowlist {
    address     = "172.168.1.1/32"
    description = "desc"
  }
}
output "ICD PostgreSQL database connection string" {
  value = "http://${ibm_database.test_acc.ibm_database_connection.icd_conn}"
}

Switching to and Scaling Hosting Models in Terraform

Select the hosting model you want your database to be scaled to. You can change this later.

To scale your Databases for PostgreSQL instance to the Shared compute hosting flavor, set the "host_flavor" parameter to multitenant. This works if you want to scale to the Shared compute hosting flavor, or if you want to keep the host flavor and scale your resources. To implement your change, run terraform apply. See the following example:

data "ibm_resource_group" "group" {
  name = "<your_group>"
}
resource "ibm_database" "<your_database>" {
  name              = "<your_database_name>"
  plan              = "standard"
  location          = "eu-gb"
  service           = "databases-for-postgresql"
  resource_group_id = data.ibm_resource_group.group.id
  tags              = ["tag1", "tag2"]
  adminpassword     = "password12"
  group {
    group_id = "member"
    host_flavor {
      id = "multitenant"
    },
    cpu {
      allocation_count = 6
    }
    memory {
      allocation_mb = 24576
    }
    disk {
      allocation_mb = 256000
    }
  }
  users {
    name     = "user123"
    password = "password12"
  }
  allowlist {
    address     = "172.168.1.1/32"
    description = "desc"
  }
}
output "ICD PostgreSQL database connection string" {
  value = "http://${ibm_database.test_acc.ibm_database_connection.icd_conn}"
}

Scale your Databases for PostgreSQL instance to Isolated compute with the same "host_flavor" parameter, set to the desired Isolated size. This command works to scale your database instance to a different Isolated Compute size, as well as to move from another host flavor to the Isolated compute host flavor. Available hosting sizes and their host_flavor value parameters are listed in Table 1. For example, {"host_flavor": "b3c.4x16.encrypted"}. Note that since the host flavor selection includes CPU and RAM sizes (b3c.4x16.encrypted is 4 CPU and 16 RAM), this request does not accept both an Isolated size selection and separate CPU and RAM allocation selections.

To implement your change, run terraform apply.

data "ibm_resource_group" "group" {
  name = "<your_group>"
}
resource "ibm_database" "<your_database>" {
  name              = "<your_database_name>"
  plan              = "standard"
  location          = "eu-gb"
  service           = "databases-for-postgresql"
  resource_group_id = data.ibm_resource_group.group.id
  tags              = ["tag1", "tag2"]
  adminpassword     = "password12"
  group {
    group_id = "member"
    host_flavor {
      id = "b3c.8x32.encrypted"
    }
    disk {
      allocation_mb = 256000
    }
  }
  users {
    name     = "user123"
    password = "password12"
  }
  allowlist {
    address     = "172.168.1.1/32"
    description = "desc"
  }
}
output "ICD PostgreSQL database connection string" {
  value = "http://${ibm_database.test_acc.ibm_database_connection.icd_conn}"
}

The host flavor parameter

The host_flavor parameter defines your compute sizing. To provision a Shared Compute instance, specify multitenant. To provision an Isolated Compute instance, input the appropriate value for your desired CPU and RAM configuration.

Host flavor sizing parameter
Host flavor host_flavor value
Shared Compute multitenant
4 CPU x 16 RAM b3c.4x16.encrypted
8 CPU x 32 RAM b3c.8x32.encrypted
8 CPU x 64 RAM m3c.8x64.encrypted
16 CPU x 64 RAM b3c.16x64.encrypted
32 CPU x 128 RAM b3c.32x128.encrypted
30 CPU x 240 RAM m3c.30x240.encrypted

CPU and RAM autoscaling is not supported on Cloud Databases Isolated Compute. Disk autoscaling is available. If you have provisioned an Isolated instance or switched over from a deployment with autoscaling, keep an eye on your resources using IBM Cloud® Monitoring integration, which provides metrics for memory, disk space, and disk I/O utilization. To add resources to your instance, manually scale your deployment.