Cloud-to-cloud migrations: Making the user experience seamless through coexistence

A survey published by Gartner in August 2018 found 25 percent of public companies have transitioned to a cloud email platform, with those rates even higher among private companies and SMBs. Now that so many businesses have migrated from on-premises applications to the cloud, the market is now seeing a sharp uptick in the number of cloud-to-cloud migrations, reaching parity and even surpassing on-prem to cloud moves.

One of the biggest drivers of cloud-to-cloud migrations are mergers, acquisitions and divestitures. In this scenario, the buyer needs to merge those new users and data into their environment. In the likely chance the business is running Office 365, this would require performing a tenant to tenant (T2T) migration of workloads including mailboxes, OneDrive or SharePoint instances, personal archives or Personal Storage Tables (PSTs), and any other data associated with users the cloud office suite.

If it sounds simple, it’s not. Migrations are complex, time-intensive IT projects with high costs for failure. Let’s look at some of those barriers and how to overcome them by creating and executing a successful migration plan.

No Shortage of Challenges

Preserving business continuity is crucial to any cloud office migration -- the goal is a seamless transition with zero downtime or disruption to business. But for the intrepid managed service provider or IT pro, what’s standing in the way? Plenty of things.

Many companies run round-the-clock, global operations with mobile employees working offsite. When factoring those continuous work schedules, there are few opportune times to launch a migration. Workers expect their email accounts, calendars and documents migrated completely, while business owners want the entire process completed with zero impact on operations and productivity.

There’s not always the option to move everyone at once -- a strategy we refer to as the "big bang."

A popular strategy for T2T scenarios following an acquisition is a batched approach: migrate specific groups of individuals or departments at a time to avoid interrupting critical functions, tasks or projects.

When this occurs, users from the same organization will exist on both the Source and Destination. This can create significant communication challenges between these employees. That’s why coexistence between these tenants is a critical part of a successful migration post-acquisition.

When Coexistence Is Key

The two biggest challenges facing users in this scenario are making sure emails are routed to the correct inboxes and that the users have visibility into their colleagues’ calendars -- their "free/busy" status. When coexistence is enabled, these users don’t have to worry about knowing whether their colleague has been migrated or not. It’s business as usual.

Here’s how it works:

  • First, the IT team reads the Source mailbox and creates contacts on the Destination, which allows free/busy calendar information and availability to be shared among users.
  • Next, the IT team places a forward on the Destination mailbox that points back to the Source mailbox, in case a message is emailed to the new mailbox before cutover.
  • Then the IT team migrates the data from the Source to the Destination, while the user is still working in the Source mailbox.
  • Finally, the IT team performs the cutover, does a final-pass migration, and reverses the forwarding so the Source mailbox forwards to the Destination.

The advantages of coexistence are plenty. Any user who still hasn’t been migrated is able to send email to a user who has been migrated. In fact, migrated and non-migrated users can continue to exchange communication regardless of migration status throughout the entire process. The only clue anything has changed is when users are asked to enter their password after their migration is complete.

In short, enabling coexistence between two Office 365 tenants throughout the migration prevents disruption to the end user while offering the service provider or internal IT team greater flexibility to complete the transition.

Pay Attention to Domain Names

Challenges associated with a T2T migration depend largely on whether there is a change in domain name. Because Microsoft only allows a domain to exist on one Office 365 tenant at a time, the batched approach with coexistence outlined above isn’t an option.

One strategy for speeding up same-domain migrations is to pre-stage older mailbox data -- such as emails older than 90 days -- to accelerate data transfer speeds and minimize inevitable downtime while the domain is transitioned to the Destination. Another option is to do it the opposite way: Move the newest content first and perform the cutover, and then run delta passes to move older emails and calendar items.

As with any migration, the key to success is careful preplanning that maps out the entire migration, having realistic timelines, keeping technical resources on hand throughout to guide the process, and maintaining a clear line of communication with end users. Do these things and you’ll have a successful transition to your desired Destination.

Image Credit: Lightspring / Shutterstock

Kelsey Epps is a senior technical partner strategist with BitTitan. A 20-year IT industry veteran, Kelsey works with MSPs and IT specialists on the technical pre-planning aspects of the most complex migrations projects.

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