What is the best practices on Archival of contents after OneDrive migration from file server

[Avian 1]

Hello

We are in process of migrating contents from various file server to user specific OneDrive for Business. After migration we are making user folder as read-only and keeping the archive next 90 days on file server after migration.

Now we want to archive the contents after 90 days, for this we want to understand how much data to be archived, should we archive the data to Azure or it should be archived in some centralized file server and user can access it in read mode.  

Please advise what should be the best practice to archive the data, and which process is cost effective or any article available on this.

Avian

[#2]

Is it not an option to use current file servers to keep the content in read only mode for those 90 days?

[#3]

Yes, we are providing 90 days option in read mode. But I want to understand process after 90 days archival?