VMWare DRS - What is it?

VMWare DRS (Distributed Resource Scheduler)


Distributed Resource Scheduler or DRS is an add-on feature of VI 3 infrastructure that is managed by Virtual Center. DRS allow balancing the CPU and memory resources of the virtual machines or VMs and the other ESX servers in the cluster.

DRS helps to balance the CPU and memory of its cluster members based on the configured resource pool policies such as shares, reservations and limits. The hosts and VMs are continuously monitored by the virtual center. Based on the configuration, if there is any imbalance of resources, the VMs are moved across the hosts in the DRS cluster.

The placement of VMs across the cluster can be configured based on,

Affinity and anti-affinity rules – Rules that define which VMs can run together (affinity) and cannot run together(anti-affinity) in any given host. A perfect example for anti-affinity would be placement of a SQL server and Exchange server. At any point of time, you don’t want to place both the servers in the same host.
VMotion compatibility – VMotion has it’s own set of requirements to move the VMs across the hosts. For example, if a VM that has a local network (not connected to any physical adapter) cannot be moved using VMotion.

Based on the environment and needs DRS automation can be set to the following levels:
Manual – DRS only provides recommendation on placing the VMs. Manual action is required to place them on recommended hosts
Partially automated – During VM power-on, they will be placed on the DRS recommended hosts. VM migrations caused by resource imbalance will be recommended by DRS but won’t be moved automatically
Fully automated – DRS automatically places the VM during power-on also during resource imbalance on the DRS recommended hosts. The migration threshold level can also be set with this level between conservative and aggressive using a slide bar.

Few factors to consider about DRS:

There can be up to 32 hosts per DRS cluster
It’s recommended to use combination of DRS automation levels based on the critical nature of VMs. To accomplish this, the cluster level DRS automation can be overridden by the VM level automation setting.
In the manual and partial automation level, it is important to pay attention to the number of stars on the recommendation. A 5-star recommendation should always be considered and applied.
Swap file location for the VMs is configurable in the DRS cluster and it is recommended to keep the swap file in the same directory in the VMFS datastore for performance reasons. Choosing to keep the swap file of the VM in the datastore based on the host setting will result in a poor VMotion performance during a resource imbalance.

More details about DRS cluster can be found here:


www.vmware.com/pdf/vmware_drs_wp.pdf

http://pubs.vmware.com/vi301/resmgmt/wwhelp/wwhimpl/common/html/wwhelp.htm?context=resmgmt&file=vc_cluster_concepts.6.6.html

Cloud Computing- The future of computing? – Part I

Cloud Computing – A buzz word that is murmured everywhere by the IT folks or even non-IT people recently. This article describes what it really means to the beginners those who are interested or looking into cloud computing.

Cloud computing is a computing model where the infrastructure and the application (even the platform) is offered as a service over the Internet. The infrastructure cloud could include servers and storage and the application cloud includes various applications such as web and databases.

Even though cloud computing can be classified into many different types the major ones are Public clouds, Private clouds and Hybrid clouds.

Public clouds – As the name suggests, it is usually offered by a company who has invested a lot building their datacenter and offering a part of its infrastructure and platform for a monthly fee. Amazon, Terremark, RackSpace and Google are great examples of public clouds

Private clouds – This is something that enterprises build by themselves to be utilized across their organization. This allows them to consolidate their servers (and storage) as a single entity that can be offered to their different business units as needed. There is an interesting article from Network World can be found here.

Hybrid clouds – This is an emerging area of cloud computing where the private and public clouds can be integrated. There are many factors such as security and application compatibility needs to be considered in this model

Driving factors for cloud:

The recent developments in the virtualization technology gave a big boost to cloud computing. There are many reasons that drive the cloud computing. Some of them are,
Rapid deployment of servers and applications
Easier scalability
Allowing IT to run as a cost center by running multiple datacenters as single entity which can be shared and charged back based on usage
Cost efficient pay as you go pricing model

Apart from its benefits, there are still few concerns about the security, compliance and the application compatibility with cloud computing. However, they are being addressed by the cloud vendors.

Let’s look into some of the cloud services in-depth in Part II