This content is part of the Essential Guide: Guide to app portability and interoperability
Evaluate Weigh the pros and cons of technologies, products and projects you are considering.

Improving cloud interoperability with application migration tools

Application migration tools can improve communication between clouds and make it easier for IT shops looking to move apps.

Cloud interoperability goes beyond matters like cloud application programming interfaces and virtual machine image format conversion. It is primarily about application migration; moving them back and forth between private clouds and public clouds or from a public cloud to another public cloud. Application migration among clouds allows users to select best of breed cloud technology and avoid lock-in, but it's not possible without tools that facilitate communication between different cloud vendors and services.

Each cloud provider decides which hypervisors, storage models, network models, management tools and processes they are going to work with. This means limited control of the environment for developing and deploying applications; the decisions made by a cloud provider affect what you can and cannot do in a cloud.

Vendors do not want clouds to become commodity products because they do not want to compete on price alone.

Even if there was an open standard cloud API that all vendors used, only part of the problem would be solved. Only relatively simple applications can be migrated to a target cloud without some difficulties. Most depend on services such as a directory infrastructure, identity management and databases, and every component of the application must be determined and reproduced or replaced in a target cloud. This is true for all application dependencies.

But there are some potentially good options available to reduce the issues associated with cloud interoperability and application migration. CloudSwitch, Racemi DynaCenter 4.0 and Citrix NetScaler Cloud Bridge are three tools that help move applications among clouds. These tools do not require modifications, and they allow applications to be managed as though they are still running in a private cloud.

Tools to facilitate application migration in clouds

Some customers may not want to go through the process of trying to make an application work in a target cloud environment, given the differences between environments. From the user perspective, the applications should behave as though they are still being delivered from the enterprise data center (private cloud). The target cloud should be a transparent extension of the source cloud.

If we can give the virtual machine in the target cloud exactly what it wants to see independent of the hypervisor, the cloud environment it is on, etc., then application migration is easier. This is what products like CloudSwitch, Racemi DynaCenter 4.0 and Citrix NetScaler Cloud Bridge offer.


CloudSwitch facilitates multi-tier application migration in the cloud with its Cloud Isolation Technology, which is a virtualization technology layer that automatically runs on top of the cloud provider’s hypervisor and beneath the user’s operating system. The virtualization layer feeds the virtual machine exactly what it wants to see. It does not require anything special from the cloud provider, and it is run on behalf of the customer to protect and isolate the customer’s environment in the cloud.

As an image is migrated, the CloudSwitch tool does a number of things automatically:

  1. It moves the data associated with the migrated application.
  2. It encrypts the data.
  3. It maps the application into the cloud, so it is running in the target environment with the same exact configuration the customer had in his home environment.
  4. It launches an encrypted tunnel with a layer-2 bridge to the target cloud so the cloud resources stay integrated with the data center's security and networking while maintaining IP and MAC addresses.

The customer does not have to modify anything, as the CloudSwitch tool handles all of the encryption and maintains network connectivity. From the user's point of view, managing the new virtual machine running the migrated application in the target cloud is the same as managing the application in the source cloud. You can think of this as giving the customer his own private cloud within the target cloud.

If you create new virtual machines in a cloud provider such as Amazon or Terremark, the CloudSwitch tool provides the capability to take the virtual machine back to your data center or move it to another cloud. CloudSwitch lets customers migrate existing applications and provision new ones in the cloud according to the user’s specific configuration requirements.

Racemi DynaCenter 4.0

Racemi takes a different approach to migrating applications than CloudSwitch. It involves capturing a server, physical or virtual, in one environment (data center or cloud) and then deploying it in a target environment (data center or cloud). The source and target hardware servers must be binary compatible, and the target hardware must have drivers for the operating system (guest operating system) that is being dropped onto the target hardware.

An important component of the Racemi's application migration is a management appliance. It can be viewed as a black box that runs software and receives reports from managed servers on things like configuration settings. The location of the management appliance may be in the private data center of a customer or on a public cloud provider’s premises.

To capture an application, an administrator connects to the Web server on the managed appliance and pulls down an agent. The agent software must be installed on every physical or virtual server that is involved. Once the agent is installed, it stores the hardware and software environment of the server (to be captured) in an image depot. When the captured server image is later deployed, the hardware and software environment of the source server are retrieved.

To deploy a captured server, a virtual machine is created in the target environment. Through a bit of trickery, Racemi then accesses the virtual machine and replaces the software placed in the virtual machine by the cloud provider. When the virtual machine is rebooted, it is running off a RAM disk-based image that contains Racemi software. The virtual machine reports back its hardware environment in the cloud provider. The management appliance has access to both the captured server environment and the target server environment and begins a mapping process between the two environments. Once this mapping process is completed, the capturing-deploying activity is complete, and the application has been migrated to the target environment.

The secret sauce of DynaCenter 4.0 is its ability to compare the configuration of the source and target cloud environments and make necessary changes in flight to make the captured server compatible with the target environment.

Citrix NetScaler Cloud Bridge

NetScaler is built around the concept of a cloud bridge. A cloud bridge makes cloud-hosted applications appear as though they are running on one contiguous enterprise network by extending the source cloud to the target cloud in a hybrid cloud environment.

The NetScaler Bridge contains a secure tunnel that provides connectivity between the clouds and allows data and information to be moved without a loss of security. It also offers transparent access to application services such as DNS and LDAP that are hosted in the source cloud. And it creates an overlay network that is a logical extension of the source cloud DMZ to make the settings on the target cloud VLAN look similar to those on the DMZ VLAN.

One of the issues that must be resolved for this type of tool, CloudSwitch and Racemi DynaCenter 4.0 included, is application performance. The application runs in the target cloud, so latency and other overhead must be monitored. This can be done with NetScaler Cloud Bridge using techniques such as caching and wide-area file services (WAFS). WAFS allows applications and users to access and share files globally at LAN speeds over the WAN.

With secure networking in place and application performance handled, applications can be moved to a target cloud without changes to the application and processes, along with no need to retrain users on how to access applications. With NetScaler Cloud Bridge, you get this plus the ability to keep your data and directory services in a secure, on-premises location.

Cloud application migration tools roundup

The three application migration tools -- CloudSwitch, Citrix NetScaler Cloud Bridge and Racemi DynaCenter 4.0 -- focus on not only making application migration simpler but presenting the view that managing the migrated application in the target cloud is the same as managing the application in the source cloud. None of these tools require any changes to an application, which means less variations of each application will be created as they bounce around from cloud to cloud.

It is clear that users do not want to be locked in to a single cloud provider or cloud vendor. Cloud users and vendors are far apart on the issues of open standards and cloud interoperability. Joe Skorupa, a Gartner vice president, has noted that even if an open cloud standard should come to pass, every provider will still continue to implement its own proprietary enhancements to differentiate its wares from the competition. Vendors do not want clouds to become commodity products because they do not want to compete on price alone.

Tools like these, however, give you more freedom to switch providers as your cloud computing needs and business requirements change.

About th author:
Bill Claybrook is a marketing research analyst with over 35 years of experience in the computer industry with the last dozen years in Linux, Open Source and Cloud Computing. Bill was Research Director, Linux and Open Source, at The Aberdeen Group in Boston and a competitive analyst/Linux product-marketing manager at Novell. He is currently President of New River Marketing Research and Directions on Red Hat. He holds a Ph.D. in Computer Science.

Next Steps

Resolving cloud application migration issues

How providers affect cloud application migration

Legacy application migration to the cloud and security

Strategies to consider before moving apps to the cloud

Dig Deeper on Cloud application migration

Start the conversation

Send me notifications when other members comment.

Please create a username to comment.