DRS (Distributed Resource Scheduler) is an advance feature of the vCenter which helps to balance the load on the cluster in automated way. DRS helps to make intelligent allocation of vm resources to ensure the optimal performance within the virtual infrastructure.
DRS is an very useful utility which helps vCenter to automate the balance of the load in the cluster so that servers can run smoothly without any interruptions. DRS works on the cluster created in the vCenter Server all the Hosts that are added into that cluster are monitored by the DRS to balance the load on the cluster. DRS helps the cluster to place the vm on the host which is free. It automatically calculate the resource usage on the cluster & makes placements & also provide the recommendations. DRS continuously monitors the load by default every 5 minutes. If it finds the cluster is imbalanced then it will automatically decide which host should run the vm or it will make an placement & ask you for recommendations for vMotion. DRS uses vMotion to migrate vm’s inside the DRS cluster. Main Benefit of DRS is to ensure that all the vm run optimally with assigned resources.
Benefits of DRS :-
- Balance Load on the cluster & hosts
- Automated Migration of VM
- Efficient & Optimal use of Server Hardware
- Guarantee Service levels
- Continuous monitoring of the Hardware Usage
- Prioritizing the hardware resources depending upon the importance.
- Helps to avoid Downtime
Requirements for DRS :-
- vSphere Enterprise or Enterprise Plus License
- Shared Storage
- CPU Compatibility or EVC enabled for vMotion
DRS helps the IT Team to manage & use the resources in the efficient way by utilizing all the resources in correct manner while balancing the load. DRS is a process which runs inside the vCenter Server so to use the DRS you will require the vCenter Server. DRS has 3 different levels of automation’s . Manual , Partially Automated & Fully Automated .
So let’s see Each mode one by one :-
In Manual always require user’s interactions to do the placements & Migrations of the VM. It does not do anything itself instead it will ask the user & provide the recommendation & depends on that user will approve & apply the recommendation for the placement & migration of VM. When you first power on the VM it will always ask you for the placement of that VM because DRS is running in the Manual Level. It will also give you the recommendations about the Migrations of VM in case of imbalanced cluster.
You can check the below screenshot of the Recommendations when the Manual Level is enabled in the DRS cluster:-
Partially Automated :-
Partially Automated will work in the partially automated way. When this level is activated vm will be placed automatically when powered-on & DRS will provide the recommendations for migration of that VM. So in short in this level placement of the vm will be done by DRS but migration of VM will require user interaction. When Partially Automated level is enabled you will get the recommendations about the migrations in Cluster > Monitor > vSphere DRS > Recommendations .
When you see any recommendations you just need to click on Apply Recommendations to approve the it.
In the below screenshot you can see how you get the DRS Recommendations when Partially Automated Level is enabled.
Fully Automated :-
As the name suggests you can easily understand this level. This works in the fully automated process & does not require any user interactions. It will check for the imbalanced cluster or load on the cluster & according to that it will automatically Place or Migrate the VM to the host to balance the load of the cluster. In Fully Automated you will see sometimes that VM is migrated within the cluster automatically without any user interactions. Fully Automated is the best to use automation level with DRS because it will automatically do everything without any user interactions. You just have to enable the DRS & set DRS to Fully Automated that’s it now all the load of the cluster will be handled by the DRS intelligently.
Checkout Our Post on DRS:-
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Graphic Credits to VMware.