We run migrations in waves rather than a single big-bang cutover. Each wave has a scoped audience, a rollback plan, and a success definition before a single file moves. We pair Microsoft’s own tooling with purpose-built third-party tools where they save weeks, and skip them where they don’t. Tenant-to-tenant consolidations after an acquisition follow the same wave model, devices included. The largest to date moved 2 PB for a national healthcare system.
Typical engagements run 8 to 20 weeks depending on scale and source complexity. Every migration leaves the client owning the runbook, so the next wave doesn’t need us.