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VMware Cluster Rules Manager (CRM) Fling – cool tool to manage DRS rules

  • April 18, 2023
  • 10 min read
IT and Virtualization Consultant. Vladan is the founder, and executive editor of the ESX Virtualization Blog at He is a VMware VCAP-DCA and VCAP-DCD, and has been a vExpert from 2009 to 2023.
IT and Virtualization Consultant. Vladan is the founder, and executive editor of the ESX Virtualization Blog at He is a VMware VCAP-DCA and VCAP-DCD, and has been a vExpert from 2009 to 2023.

VMware Fling is a platform for experimental and innovative tools that help users to enhance their virtualization and cloud computing experience. The VMware Fling that we’ll highlight today is called Cluster Rules Manager (CRM), which provides an intuitive user interface to create and manage DRS (Distributed Resource Scheduler) rules within a vSphere cluster.

The Cluster Rules Manager (CRM) is an easy-to-use tool that allows vSphere administrators to create and manage DRS rules that can automate the process of balancing workloads across a vSphere cluster.

Connection from the Fling to vCenter server is encrypted so no reason to worry about passing some confidential information in clear text over the network.

With CRM, users can set rules based on specific criteria such as virtual machine affinity, anti-affinity, and host affinity. In addition, users can also specify the threshold for each rule, which helps to avoid overloading hosts and underutilizing resources.

With vSphere, If you create a DRS affinity rule for your cluster, you can specify how vSphere HA applies that rule during a virtual machine failover.

For those of you who doesn’t know, there are two types of rules for which you can specify vSphere HA failover behavior are the following:

  1. VM anti-affinity rules force specified virtual machines to remain apart during failover actions.
  2. VM-Host affinity rules place specified virtual machines on a particular host or a member of a defined group of hosts during failover actions.

When you edit a DRS affinity rule, you must use vSphere HA advanced options to enforce the desired failover behavior for vSphere HA.

  • HA must respect VM anti-affinity rules during failover — When the advanced option for VM anti-affinity rules is set, vSphere HA does not fail over a virtual machine if doing so violates a rule. Instead, vSphere HA issues an event reporting there are insufficient resources to perform the failover.
  • HA should respect VM to Host affinity rules during failover –vSphere HA attempts to place VMs with this rule on the specified hosts if at all possible.

The Cluster Rules Manager is available as a VMware Fling, which means it is a free and experimental tool.

While VMware does not provide support for flings, the CRM tool has been thoroughly tested and validated by VMware engineers to ensure it works correctly and does not cause any issues with your vSphere environment. Admin either can deploy it in his local system or can deploy in one of the VMs. You can then connect to the web-based UI directly from the local system or over the network.

Features of Cluster Rules Manager

The Cluster Rules Manager has several features that make it an essential tool for vSphere administrators:
1. Audit anti-affined VMs – you can audit critical VMs for anti-affinity across vCenter server.

Get VM-Rule Association

Get VM-Rule Association

2. Importing capability – Importing DRS affinity rules from multiple vCenter servers

3. Exporting capability – The software is able to export DRS affinity rules to new vCenter from the vCenter for which DRS rules are already imported. It has a real time complete DRS rule report containing various intelligent metrics. The user can choose to generate this report on the vCenter server level, datacenter(s), or cluster(s) level. This report can be exported.

4. Intuitive User Interface – The CRM tool has a simple and intuitive user interface that allows administrators to create and manage DRS rules easily. The interface provides detailed information about each rule, including the rule type, rule name, the threshold value, and the virtual machines or hosts associated with the rule.

5. Real time VM-Rule association report – you can specify a VM and the report give you all the associated rules with this VM. You can download the report for an offline consultation.

Generate report

Generate report

How to Install and configure Cluster Rules Manager

Using the Cluster Rules Manager is easy and straightforward. You should follow the installation PDF which basically consists a setup a local system with a DB and web server, then launch the installation script.

You can use the existing database server, a local database for the Fling to be deployed or an external database server. A Microsoft SQL, MySQL or Oracle 11GR2 are supported DBs.

The following steps outline the process of creating and managing DRS rules with the tool:

  1. Download Fling war (crm.war) file as well as self-signed certificate (crminstallationkeystore.jks) from fling website.
  2. Copy the downloaded war file under <TOMCAT_ROOT_DIR>\webapps\
  3. Copy the downloaded self-signed certificate crminstallationkeystore.jks and paste into any location under tomcat-deployed machine.

After, you’ll need to create <connector> tag, but it’s better if you follow the Installation PDF which is part of the download bundle.

Benefits of using Cluster Rules Manager

The Cluster Rules Manager provides several benefits to vSphere administrators, including:

  1. Increased Efficiency – The tool allows administrators to automate the process of balancing workloads across a vSphere cluster, which increases efficiency and reduces manual intervention.
  2. Improved Performance – By creating and managing DRS rules, the Cluster Rules Manager helps to ensure that virtual machines are running on hosts with adequate resources, which improves performance.
  3. Better Resource Utilization – The tool helps to avoid overloading hosts and underutilizing resources, which leads to better resource usage.

Final Words

The CRM tool from VMware offers some cool auditing anti-affinity across VMs within your vCenter server. The fact that you can import those rules from multiple vCenter servers makes it pretty flexible. Same for the exporting capability, you can export those DRS affinity rules to a new vCenter server.

Hey! Found Vladan’s article helpful? Looking to deploy a new, easy-to-manage, and cost-effective hyperconverged infrastructure?
Alex Bykovskyi
Alex Bykovskyi StarWind Virtual HCI Appliance Product Manager
Well, we can help you with this one! Building a new hyperconverged environment is a breeze with StarWind Virtual HCI Appliance (VHCA). It’s a complete hyperconverged infrastructure solution that combines hypervisor (vSphere, Hyper-V, Proxmox, or our custom version of KVM), software-defined storage (StarWind VSAN), and streamlined management tools. Interested in diving deeper into VHCA’s capabilities and features? Book your StarWind Virtual HCI Appliance demo today!