Status	Pending Stakeholder Review
Owner	Gautier Todeschini
Stakeholders	James Kyndt, Frank Bolata, Boris Foiselle

Issue

There are several ways to migrate Syensqo users and data towards the Microsoft environment, all have technical complexities and user impacts.
Syensqo is too large to consider a “big bang” approach while ensuring low disruption, and a migration by wave will create a coexistence period of 3 to 5 weeks (when both Google Workspace and Microsoft 365 will be used simultaneously).
Prolonged coexistence can lead to increased complexity, higher support costs, user confusion, and potential security risks.

Therefore, it is critical to identify a migration approach that minimizes the duration of dual-platform usage while ensuring a smooth transition, business continuity, and minimal disruption to employees.
The decision to be made is to select the most effective migration strategy that reduces the coexistence period, addresses technical and operational requirements, and supports user experience.

Recommendation

After careful consideration of the risks and challenges associated with prolonged coexistence of Google Workspace and Microsoft 365, it is recommended that Syensqo adopts a wave-based migration approach rather than a "big bang" migration.

Rationale for Wave-Based Approach

Controlled Transition: Migrating users and data in defined waves allows for better management of technical and operational complexities.
Risk Mitigation: Issues can be identified and resolved early in smaller groups, reducing the risk of widespread disruption.
User Support: IT and support teams can focus on smaller user groups at a time, providing more effective training and troubleshooting.
Business Continuity: Critical business functions can be prioritized and migrated at optimal times, minimizing impact on day-to-day operations.
Reduced Coexistence Period: While not as immediate as a big bang, a well-planned wave approach can still significantly shorten the coexistence period by enabling parallel preparation and execution.

Background & Context

By following this strategy, the organization aims to achieve the following:

Enhance collaboration and productivity by consolidating services under Microsoft 365.
Ensure data integrity and compliance with enterprise standards.
Minimize risks and downtime during the migration process.
Deliver a seamless user experience.

Assumptions

All data will be migrated (emails, personal documents in My Drive, Shared document in Shared Drive and Aodocs

Constraints

Microsoft Fast track imposes the following contraints

Max amount of data migrated
Max number of accounts migrated
etc...

Impacts

Business Rules

Options considered

Option 1: One Shot Cutover

Option 2A: Migration by waves - GBU/BSA/GBS driven

With this construct of waves based on GBU’s, we primarily focus on who is working together therefore we migrate complete GBU’s and GBU’s who collaborate a lot. So the people in one wave will have less impact collaborating and communicating. As a second factor we can also group GBU to fill the waves to the 5500 user threshold.

Avanade has created an initial proposition of the order and grouping of the GBU’s in 4 actual Users/GBU waves and 1 final wave with users that cannot be attached to a GBU and the Shared Mailboxes.

We will further align on the best combination and order of the GBU waves taking into account the above guidelines.

Option 2B: Migration by waves - regional approach driven

With this construct of waves based on region, we primarily focus on aligning the migrated people on time zone’s

One of the key reasons for this approach lies in meeting room and calendar functionality. Once a user is migrated to Microsoft 365, their mailbox and calendar no longer reside in Google Workspace. From that moment onward:

- They must book and use meeting rooms that are now hosted in Microsoft Exchange Online.
- Any meeting rooms remaining in Google Workspace will no longer be accessible or reliable for migrated users.
- If users from the same physical office location or country are split across platforms (e.g., HR and IT are migrated but Finance is not), it creates confusion and technical issues with room bookings, calendar invites, and shared availability.

Therefore, to maintain calendar integrity and ensure reliable resource booking, we migrate complete countries together.

Evaluation

	Option 1 One Shot Cut Over	Option 2A Migration by waves - GBU/BSA/GBS driven
Technical Feasibility	16 K active users (20 K active Mailboxes ~229 TB mailbox + ~181 TB MyDrive) 3194 active shared drives (~ 63,6 TB Shared Drives)+ 2116 AODocs Lib. (13,7 TB)	Can tailor the waves to adhere to the constraints imposed by Microsoft Fastrack
User Impact	All of Syensqo is impacted at the same time "bank aid" approach in some cases can be seen as a better approach to change management	Collaboration between users of the same GBU will be easier as they will not have any coexistence period within Should collaboration need to occur with a GBU/BSA or GBS that has not yet migrated users will need to follow coexistence recommendation
Support Impact	Little possibility to ramp up the IT Support organisation, over the weekend they need to go from supporting fully one tool to another one	Ramp up of full support through a controlled process Will be supporting the users in a same country on two different platforms
Operational Complexity
GBU/BSA/GBS Feedback
Cost