Virtual Instances - Placement groups

Placement Groups Overview

If you run multiple Compute Instances, you may want the guarantee that none of them run on the same physical hypervisor. This is a requirement for a lot of workflow from API redundancy to Kubernetes pods. On Scaleway, this is achievable by querying the api-metadata and restarting the instances until the configuration is satisfactory. It will work but will require multiple attempts and complex automation workflows.

To make those kinds of configurations easier, we are glad to introduce Placement Groups.

Placement groups have two operating modes. The first one is called max_availability. It ensures that all the compute instances that belong to the same cluster will not run on the same underlying hardware. The second one is called low_latency and does the exact opposite: it brings compute instances closer together to achieve higher network throughput.

This documentation provides information how to:

All configuration can also be done directly from the Scaleway API. Refer to the dedicated documentation for more information how to use placement groups directly from the API.

Requirements

Setting up a Placement Group from the Console

1 . To create a new placement group, enter the Instaces section of your Scaleway Elements console by clicking on the corresponding link in the compute section of the side menu.

2 . Click on Placement Groups in the vertical menu. The placement groups description displays:

3 . Click on + Create a Placement Group to begin the configuration of the new cluster.

4 . Choose a Name of your choice for your placement group.

5 . Choose the Region in which your placement group will be created.

Important: A placement group can only contain virtual instances belonging to the same region as the placement group (for example: A group created in the region PARIS 1 may only contain virtual instances located in the region PARIS 1).

6 . Choose the placement group type. Two types of Placement Groups are available:

  • “Maximum Availability”-groups ensure that compute instances belonging to a cluster will not be running on the same physical hypervisor to maximize availability, a requirement for many workflows from API redundancy to Kubernetes pods.

  • “Low Latency”-groups do exactly the opposite and make sure instances are located as close as possible to minimize latency and achieve higher network throughput.

7 . Choose the placement group policy. Two different policies exist:

  • “Enforced”-mode enforces the application of the placement group. In case the group can not be applied, only instances on hypervisors matching the group settings will boot.

  • “Optional”-mode ensures settings of the placement group are applied whenever possible. In case the settings can not be matched, instances may boot on hypervisors not fulfilling the group policy.

8 . Select the Instances you want to add to the placement group from the drop down list. Click on Add instance to add it to the group. It is possible to add virtual compute instances within the same availability zone without any architecture or type distinction:

Impotant: Instances must be in Power-off Mode to be available to be added to a placement group.
Unfortunately placement groups are not available for Bare Metal servers.

9 . Click on Create and Launch Instances to create the placement group and start the instances within the group. If you do not want to start your instances now, click on Create a Placement Group

10 . The newly created placement group displays in the list of your groups:

11 . You can also verify if your instances are attached to a placement group from the list of your virtual instances:


Adding Instances to an Existing Placement Group

Important: Instances must be in powered-off state to be able to be added to a placement group.

From the Placement Group Configuration

1 . To add an instance to an existing placement group, click on the Placement Group tab in the compute instances section of your Scaleway Console.

2 . The list of your placement groups displays. Click on > More info to view the details of your placement group.

3 . Click on Instances to display the list of instances aggregated in this placement group.

4 . Choose the instance you want to add to the placement group from the drop-down list and click on Add instance to add it to the group.

5 . Click on > Power on next to the instances name to power-on the instance:

From the Instance Details Page

1 . From the instances list in your Scaleway console, click on the name of the instance you want to add to a placement group.

2 . On the Instance Information page scroll down to the Placement Groups section:

3 . Click on Join a Placement Group.

4 . Select the placement group to join from the drop-down list and click on Save:

5 . Scroll to the top of the page and toggle the power switch to On to boot the instance:


Removing Instances from an Existing Placement Group

From the Placement Group Configuration

1 . Click on the Placement Group tab in the compute instances section of your Scaleway Console to view the list of your existing placement groups.

2 . Click on > More info to view the details of your placement group.

3 . Click on the Instances tab to view a list of the instances aggregated in this placement group.

4 . Click on > Remove next to the instance you want to remove from the placement group:

5 . Confirm the removal of the instance from the placement group by clicking on Remove in the pop-up.

Important: Be careful when you remove an instance from a placement group as you will need to power it down, if you want to add it back to the group.

From the Instance Details Page

1 . From the instances list in your Scaleway console, click on the name of the instance you want to remove from a placement group.

2 . On the Instance Information page scroll down to the Placement Groups section.

3 . Click on next to the placement group name, then Leave to remove the instance from the placement group:

4 . Confirm by clicking on Leave in the pop-up.

Important: Be careful when you remove an instance from a placement group as you will need to power it down, if you want to add it back to the group.


Changing the Placement Group of an Instance

Important: Instances must be in powered-off state to change the instance group.

1 . From the instances list in your Scaleway console, click on the name of the instance you want to change the placement group.

2 . On the Instance Information page scroll down to the Placement Groups section.

3 . Click on next to the placement group name, then Change to change the placement group the instance belongs to:

4 . Select another existing placement group from the drop-down list and click on Save:

5 . Power on the instance by toggling the power switch on top of the instance information page. The instance boots and belongs to the new placement group now:


Modifying a Placement Group's Type

In case your requirements change, the placement group type can be modified.

Important: Before editing the placement group type, all instances of the group must be powered off.

1 . Connect to your Scaleway Console and click on Instances in the compute section of the side-menu.

2 . Click on the Placement Group tab to view a list of your placement groups:

3 . Click on .. > More info to view the details of the placement group.

4 . Scroll to the Placement Group’s type section of the page and update the type of the group.

The group type can either be:

Low Latency - These groups ensure that compute instances are located as close as possible to minimize latency and achieve higher network throughput.

or

Maximum Availability - These groups ensure that compute instances will not be running on the same physical hypervisor to maximize availability.

5 . The new group type will be applied immediately and instances of the group will boot according to the new settings once powered on.


Modifying a Placement Group's Policy

In case your requirements change, the placement group policy can be modified.

Important: Before editing the placement group policy, all instances of the group must be powered off.

1 . Connect to your Scaleway Console and click on Instances in the compute section of the side-menu.

2 . Click on the Placement Group tab to view a list of your placement groups:

3 . Click on .. > More info to view the details of the placement group.

4 . Scroll to the Placement Group’s policy section of the page and update the policy of the group. It can either be:

Enforced - This mode enforces the application of the Placement Group. In case the group can not be applied, only instances on hypervisors matching the group settings will boot.

or

Optional - This mode ensures settings of the Placement Group are applied whenever possible. In case the settings can not be matched, instances may boot on hypervisors not fulfilling the group policy.

5 . The new group policy will be applied immediately and instances of the group will boot according to the new settings once powered on.


Deleting a Placement Group

In case a placement group is no longer needed, it can be deleted from the Scaleway console. Deleting a placement group will not have direct impact on the Instances aggregated in it. Your instances will continue to run on their current hypervisors until you reboot them.

1 . Connect to your Scaleway Console and click on Instances in the compute section of the side-menu.

2 . Click on the Placement Group tab to view a list of your placement groups:

3 . Click on .. > More info to view the details of the placement group.

4 . Scroll down to the Delete Placement Group section of the page:

5 . Click on Delete Placement Group.

6 . Confirm the deletion of the placement group by clicking on Delete this Placement Group in the pop-up.

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