If a company has used cloud-based storage for important data, and wants to move the data back to storage on their own premises, there are number of complications. If multiple cloud vendors have been used, having to deal with all the different systems could make the transfer challenging. Further, since cloud storage is normally used for large amounts of data, transferring it all back can use expensive bandwidth, and the resources that will be needed to store the data and make it available may be considerable. So companies should probably not migrate data to public cloud storage without considering the difficulties of changing back if they reconsider.
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http://www.itproportal.com/2013/10/09/how-do-i-migrate-my-public-cloud-data-back-to-on-premise-storage/