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Overview

Server groups enforce placement policies that determine how a set of instances is distributed across physical compute hosts. Use server groups to guarantee high availability through host separation, improve performance through co-location, or meet compliance requirements for workload isolation.
Prerequisites
  • An active Polystack project
  • At least two compute hosts available (required for anti-affinity enforcement)
  • Sufficient server group quota

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Placement Policies

Use anti-affinity for production replicated services (web tiers, application clusters, database replicas) where a single host failure must not take down all instances simultaneously. Use soft-anti-affinity when you want best-effort separation without hard placement failures.

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Create a Server Group

1

Navigate to Server Groups

Navigate to Compute > Server Groups in the sidebar. Click Create Server Group.
2

Configure the server group

The dropdown options are:
  • affinity — instances on same physical machine (mandatory)
  • anti-affinity — instances on different machines (mandatory)
  • soft-affinity — same machine preferred (best effort)
  • soft-anti-affinity — different machines preferred (best effort)
The dialog also displays your current Server Groups quota usage (used / limit). If your quota is exhausted, the submit button is disabled.
3

Create the group

Click Confirm. The server group appears in the list.
Server group appears in the list with the selected policy.

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View Server Groups

Navigate to Compute > Server Groups. The list shows:Filter by Name or Policy using the search/filter bar.Click a group name to view the detail page, which shows the Members tab listing all instances assigned to this server group.

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Launch Instances in a Server Group

When creating an instance, expand the Advanced Options section in Step 3 (System Config) of the wizard. Select your server group from the Server Group table.Alternatively, from the server group detail page, click the Create Instance action in the More dropdown. The server group is pre-selected in the wizard.

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Delete a Server Group

Navigate to Compute > Server Groups. Click the Delete action (the first row action) on the group row. Confirm the deletion in the dialog.
Deleting a server group removes the placement constraint. Existing instances are not affected, but new launches will no longer enforce the policy.

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Next Steps

Launch an Instance

Create instances with server group placement in the 4-step wizard

Availability Zones

Understand fault domains and zone-level placement

Live Migration

Move instances between hosts while respecting group policies

Troubleshooting

Resolve placement failures and group member limit issues