Placement Rules

Overview

Zadara Cloud Services supports the creation of placement rules which determines how a VM Instance is placed on physical nodes.

Defining a rule is a 3-stage process:

  1. Use the tags attached to the VM instances and nodes to choose the placement rule type and set its parameters. There are three placement rule types:

    1. Same-tagged VM rule - VM instances with the same tag can be configured to be placed on either the same or different nodes.

    2. Different-tagged VM rule - VM instances with a specific tag can be configured to be placed on either the same nodes or different nodes as VM instances with a different tag.

    3. VM and Node tags - VM instances with a specific tag can be configured to be placed on a node with the same or different tag.

    Note

    The VM and Node tags rule can be created only by an Admin user.

  2. Define the level of rule enforcement. There are two options:

    1. Hard - VM instance placement will only be performed if the rule constraints can be satisfied.

    2. Soft - If possible, VM instance placement will be performed according to the rules. If the rules cannot be satisfied, the placement will be done anyway.

  3. Define the scope of this rule as either system-wide or for a specific project.

Note

The option to define a rule with a system-wide scope is limited to an admin user. For a regular user, the scope is that of the currently displayed project.

Placement Rule Main Window Display

  1. Navigate to the Compute > Rules view. A list of all placement rules is displayed.

  2. The following information is displayed for each rule:

    1. Description of rule type.

    2. Tags used within rule.

    3. Enforcement level of rule (hard/soft).

    4. Scope of rule (system/project).

    5. Enabled

    6. Creation Date

Add a Placement Rule

To add a Placement Rule:

  1. Navigate to the Compute> Rules view and select Add Rule. The Create VM Placement Rule window is displayed.

  2. Select the rule type (same-tagged, different-tagged, or VM and Node tagged).

    Note

    Select existing tags or create new tags in any of the Tag fields.

    Note

    VM and Node tagged rule type is available to admin user only.

  3. Select Hard or Soft enforcement.

  4. Select system or project scope.

    Note

    System scope is available to admin user only.

  5. Select OK. The new VM Placement Rule will appear in the Rules view.

Simulating a Placement Rule

  1. Navigate to the Compute> Rules view. A list of the placement rules is displayed.

  2. Select the row of the desired placement rule. A Simulate Rule icon appears in the top menu bar.

  3. Select Simulate Rule.

  4. The Simulate Rule information window will appear showing a list of VM instances potentially affected by the rule.

  5. Click OK.

Applying a Placement Rule

To apply a Placement Rule to a VM instance:

  1. Navigate to the Compute> Rules view. A list of the placement rules is displayed.

  2. Select the row of the desired placement rule. An Apply Rule icon appears in the top menu bar.

  3. Select Apply Rule.

  4. The Apply Rule confirmation window will appear showing a list of VM instances potentially affected by the rule.

  5. For VM instances which are covered by the rule, but which cannot be placed accordingly, select one of the following options:

    1. Stop the VM instance

    2. Leave the VM instance running in its current placement

  6. Click OK. A message confirming the application of the placement rule will pop-up in the upper right corner of the screen.

Note

Apply as many placement rules as needed, provided that the rule does not either duplicate, contradict or override any other rule, or that the rule itself is not overridden by any other rule.

Removing a Placement Rule

  1. Navigate to the Compute> Rules view. A list of the placement rules is displayed.

  2. Select the row of the placement rule to be removed. A Remove icon appears in the top menu bar.

  3. Click Remove. The Remove Rule confirmation window appears.

  4. Click OK. A message confirming the removal of the placement rule will pop-up in the upper right corner of the screen.