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Instead of copying all the media library files from the production environment, which could take several hours for a large media libraries of millions of files and hundreds of gigabytes of data, VIP provides a service called UnionFS.

UnionFS works by making the files for the production site available to all non-production sites in read-only mode. Files shared by UnionFS are served from the same infrastructure and have the same caching rules applied.

The non-production environment can upload a file of the same name to the same URL, and this will override the file shown on the non-production site (the production file remains untouched).


  • The non-production environment cannot delete a file on the production site. The operation will not error, but the production file will still be available and shared from the non-production environment.
  • If the file is deleted from production, it will no longer be available to be shared with the non-production environments.

Last updated: April 05, 2022