This content is part of the Essential Guide: A comprehensive guide for application migration to the cloud

Three questions to ask before you migrate apps to public cloud

Many firms assume public cloud is the best place to host all apps, but that's not always the case. Before you drink the cloud Kool-Aid, ensure it's a cost-effective move.

The public cloud is an attractive option for many enterprises because of its scalability, speed and pay-as-you-go model. But those benefits don't apply to all workloads -- in fact, some applications could perform poorly or cost more in the cloud.

This means, before you migrate apps to a public infrastructure as a service (IaaS) platform, you need to ensure the move will provide business value.

First, understand what your motivation is for a cloud migration. Do you want lower costs? Do you need more flexibility? Some businesses move to the cloud too fast, only because they assume they should, which could cause issues down the road.

Before you take the big step and migrate apps to the public cloud, start with these three questions:

How do I choose which apps to migrate?

Assess your application, and review its requirements -- for both performance and compliance -- to determine if it is a good candidate for the public cloud. Check if the application has any specific network needs or dependencies. Unless you also migrate the systems on which your app depends, including databases, latency could be an issue. Also, review an application's design before you migrate it to the cloud; those apps that frequently read and write to storage systems, for example, could end up costing you more off premises. In general, applications that are "bursty" or have frequent spikes in demand are a good fit for public cloud, while applications that run on a more consistent, predictable basis might be better left in-house.

Cloud providers offer tools, such as Azure Cloud Migration Assessment and Amazon Web Services (AWS) Application Discovery Service, to simplify the assessment process. AWS, Azure and Google also offer pricing calculators to estimate cloud costs.

In addition, determine whether the cloud provider you choose meets your security and compliance requirements. Look at where their data centers are located, especially if you have sensitive data that needs to adhere to strict compliance standards.

Which migration approach should I take?

After you decide which applications to migrate, determine a migration method. Two common options are rehost, also known as lift and shift, and refactor, also known as rearchitect.

The lift-and-shift process takes less time to accomplish than refactoring, since developers don't have to change the application's architecture or design -- they just move it as is. But while lift and shift is a simpler approach, it also has drawbacks. For example, if you migrate apps to IaaS without any modifications, they might not be able to take advantage of a key cloud feature: autoscaling. As a result, those applications will still operate the same way they would on an on-premises system -- at peak -- and the enterprise will pay for more cloud storage and compute resources than they actually use.

Two application migration models

This makes rearchitecting, or refactoring, a better option for some legacy apps -- even if it's more time-consuming and costly. Lift and shift, on the other hand, is best for cloud disaster recovery.

Do not migrate apps to the cloud too quickly -- start with apps that are the most cloud-ready and that have the least amount of sensitive data. After you run a pilot, test the application, get a feel for the process and then move onto more critical applications.

What are my options for cloud migration tools?

Migration is a complex process that comes with risk and the potential for high costs. There are both cloud provider-native and third-party tools that can aid organizations through the process. For example, the Microsoft Assessment and Planning Toolkit can help IT teams migrate apps to Microsoft Azure, while third-party tools, like Cloudyn and CloudVelox, can also play a role.

If an enterprise needs to move large amounts of data to the cloud, it can also perform an offline data migration. This requires an organization to store its data on physical disks and then ship the disks to its cloud provider. While this method might seem old-school, it can be more cost-effective than a migration via a network if you have terabytes of data. Offline data migration services from top cloud providers include AWS Snowball, AWS Snowmobile, Google Transfer Appliance and Azure Import/Export.

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