There is plenty of motivation to perform cloud-to-cloud migration or have data reside in more than one cloud. It may stem from cost considerations, unhappiness with another service or fear that a cloud provider may go out of business.
There is ample validation for those concerns. Russ Fellows, a senior analyst at Evaluator Group, recently blogged about an online code hosting service that went out of business after online attacks. In that post, Fellows offers a list of seven levels of cloud data protection, ranging from the use of a single provider, with a single account in a single location, to employing multiple cloud providers, accounts and locations. The bottom line, according to Fellows, is that the use of multiple cloud providers increases reliability, availability and resilience.
While getting your cloud data into another cloud location can be a practical idea, it can be a very labor-intensive thing to do.
First, how much data do you plan to move? That answer is important because bandwidth can be the key limiting factor. There are individual data mover tools (products), as well as services that will move the data with a charge for the amount transferred. When using a tool or service to move data (most are designed for SAN and NAS, not for the cloud), the amount of data and available bandwidth dictate the time required to complete the task -- which can be very lengthy. The cost has to be calculated on a per-case basis due to the wide variation in charges from cloud providers and migration services. Some cloud providers offer a service to export data to removable media that is then transported to another cloud provider to be imported. You should inquire about this option when choosing a provider, as it may be the most effective method when dealing with large capacities, considering both time and cost.
There is no replication between multiple cloud providers, but you may have an application (software that has to be monitored) that can perform this task. Accessing data that resides on more than one cloud is certainly possible and may be implemented with a global namespace type of solution in which another layer of software, such as a global file system or object storage system, handles the location of the data. It also could be an application-specific feature that manages the different locations. This requires more research into what a cloud provider may offer or which software may be loaded that supports this feature.
While there is no simple answer to user questions on this point, you can start by answering these questions for yourself and your provider.
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