The summary.
THE DISTINCTION THAT CATCHES PEOPLE OUT
Synchronised storage is not backup.
A file deleted, corrupted or encrypted on one device becomes that everywhere. Synchronisation faithfully propagates the problem.
Arrange a genuine backup of cloud data, separate from the service, and test restoring it.
WHAT PROVIDERS DO NOT PROTECT AGAINST
Accidental deletion discovered late, account compromise, and you ending the subscription.
Data is typically deleted after a period once you stop paying.
BEFORE MIGRATING ANYTHING
Delete what you no longer need and agree the structure first.
Migrating chaos produces chaos in a new location, permanently.
THE MOST COMMON MIGRATION ERROR
Permissions not surviving the move. Review what is shared afterwards.
FOR EMAIL MIGRATION
Record every DNS record first, update mail authentication for the new service, and keep the old mailboxes for a period.
THE COST THAT SURPRISES PEOPLE
Egress. Storing is cheap; moving data out is not.
What it would cost to retrieve everything is your exit cost. Establish it before storing large volumes.
WHAT NEVER TRANSFERS TO THE PROVIDER
Your obligations relating to personal data.
