Hello,
This is expected behavior with the current version of FSLogix Cloud Cache. When you add a new StorageProvider, the first interactive logon initiates the process of copying your profile data over to the new provider. During this time, the FSLogix App Service holds the logon session until the data has been fully synchronized between the locations. In your scenario, with a 20GB profile, it’s normal to see a delay on the first logon while the profile data is replicated. Once the initial copy is complete, subsequent logons proceed without delay because the profile is already resident in the new StorageProvider location.
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