As an Infrastructure-as-a-Service provider, Bluelock sees a lot of migration of applications. Migration is occurring from physical servers to cloud, from private cloud to public cloud and back to private cloud from public cloud.

Migration can be tricky and a poor migration strategy can be responsible for costly time delays, data loss and other roadblocks on your way to successfully modernizing your infrastructure.

While each scenario is different, I'd like to identify three key best practices that will help your team create a solid, successful plan for migrating your application.

Even before you begin to move your application, there's a lot of best practice that goes into choosing which application to migrate to the cloud. Regardless of whether you are migrating that app to a public cloud or a private cloud, you should assess the app for data gravity and connectivity of the application.

Best Practice: Understand the Gravity of Your Data
Data Gravity is a concept first discussed by Dave McCrory in 2010. It's the idea that data has weight and the bigger the data is, the harder it is to move. The bigger the data, the more things are going to stick to it.

McCrory states in his original blog post about Data Gravity, "As data accumulates (builds mass) there is a greater likelihood that additional Services and Applications will be attracted to this data."

McCrory goes on to explain that large data can be virtually impossible to move because of latency and throughput issues that develop upon movement. On his website, datagravity.org, McCrory explains that to increase the portability of an application it should have a lower data gravity.

When moving tier one applications from a physical datacenter to a private or public cloud, we have to take data gravity into account because it will impact the migration.

As you are talking about migrating an application, you can think of the full stack of components as a single VM or a group of VMs that are a vApp (see Figure 1).

Think of a VM with an OS. If we were to migrate that entire VM to the public cloud, we're copying anywhere from 8-20 GB of data with that OS for no reason at all as the cloud you're migrating the app to might already have the OS available to it.

Rather than transferring the data for the OS, whenever possible use metadata instead to describe what OS you want and the configurations using a template or an image on the public or private cloud side. The same metadata concept can be applied to middleware instances too.

What we're left with is our actual data and what the app is. The app is static and static info is easy to move because you can copy it once. There's no need to replicate.

The most difficult part of the migration is the data, however. There's no easy way to shrink down the data, so you need to evaluate the weight of the data in the app you're considering migrating.

Especially if you're a high transaction company, or if it's a high transaction application, as that would be a lot of data to replicate. The data of the app constitutes 99% of the data gravity of the application.

Part of the best practice of understanding the gravity of your application is to understand the ramifications of moving a tier one application with a large amount of data and establish where the best home for that application is.

Another aspect that you should evaluate as part of your pre-migration plan is to determine how connected your VM or vApp is to other apps.

If you have a lot of applications tightly coupled to the application you want to migrate, the cloud might not be an option for that application, or at least only that application.

Best Practice: How Connected Is Your App?
Beyond what applications are connected to the app you want to migrate, the important aspect to evaluate is how coupled the application in question is to other applications, and how tight or loose of a couple they are.

Does your application have data that other applications need to access quickly? If so, a move all or nothing philosophy is your best option.

If you have an application that is tightly coupled to two or three others, you may be able to move them all to the cloud together. Because they are still tightly coupled, you won't experience the latency that would occur if your cloud-hosted application needed to access a physical server to get the data it needs to run.

A step beyond identifying how many apps are tied to the application you wish to migrate, work next to identifying which of those applications will be sensitive to latency problems.

How sensitive it can be should be a consideration of whether you should migrate the app or not.

To be able to check this best practice off your list, be very sure you understand everything your application touches so you won't be surprised later, post-migration.

The final part gets down to the nitty gritty... choosing the correct migration strategy.

Best Practice: Pick Your Migration Strategy.
Your best-fit migration strategy will be a function of the features of the application.

Option one is data migration of just the data. This is typically the correct choice for tier 1 and 2 applications.

Let's say you are able to migrate your VM or vApp. But, it's constantly changing and if it's a tier one application, we may not be able to afford a lot of downtime. Typically, we'll have to invoke some sort of replication.

Replication is an entirely separate subject, but when I think of replication, I think of the size of the data, the rate of change and the bandwidth between our source and target.

Without going into too many details of replication, let's assume you use some sort of SQL or MySQL program for database replication. What you've done is set up your new cloud to have this OS provision. You've got a MySQL provision and the two SQLs are talking to each other and replicating the data.

Option two for migrating your application is machine replication. This is best for tier 1 and tier 2 applications that can afford some downtime. It involves stack migration. There is less configuring in this scenario, but there is more data migrating.

Option two is best if you're moving to an internal private cloud. You will be able to replicate the entire stack because you have plenty of bandwidth to move stuff around.

It's important to note the portability of VMware, because VMware allows you to package the entire VM/vApp, the entire stack, into an OVF. The OVF can then be transported anywhere if you're already on a virtualized physical server.

Option three involves cold P2V migration. You typically see this for tier 2 and 3 apps that are not already virtualized.

The concept involves taking a physical app and virtualizing it. VMware has a VMware converter that does P2V, and it's very easy to go from a physical to a private cloud using P2V. It is, however, an entirely different set of best practices.

In option three, there is no replication. Those apps can also be shipped off to a public cloud provider to run in the public cloud after being virtualized.

A final path some companies take is to treat it as a Disaster Recovery (DR) scenario. Setting up something to basically do replication from one machine to another. Replicate the entire stack from point a to point b, and then click the failover button.

Each application, and migration strategy, is unique, so there is no detailed instruction manual that would work for everyone. The best strategy for some applications may be to stay put, especially if you find that steps one and two of the pre-migration evaluation is closely connected or especially weighty. To truly enjoy the benefits of cloud, you want the right application running that you can leverage to the fullest extent.

When planning your migration strategy, ask for help from those who are familiar with similar use cases and plan and evaluate extensively to save yourself a lot of time, money and headaches that come from rushing into a migration without a strategy.