Apple’s iCloud runs on two services from its biggest competitors, Microsoft’s Azure and Amazon’s elastic cloud, reports The Register.

Sources tell the site that both Microsoft and Amazon were instructed to remain mum on the iCloud deal. Amazon’s elastic cloud is already established as a go-to service for any company that wants to offload data and other resources, but the deal serves as a major validation for Microsoft’s Windows Azure.

Writes The Register: “iCloud puts Azure into a different league, given the brand love for Apple and the Apple management’s fanatical attitude to perfection. It is a “huge consumer brand, a great opportunity to get Azure under a very visible workload,” our sources told us.”

Apple is likely aiming to avoid potential iCloud outages by selecting two cloud suppliers. The company has already had the headache of dealing with outages for its MobileMe service, which relied on a single external provider. Apple is also building its own massive data center in North Carolina, which could eventually take over some of the load for iCloud.

The Register notes that iCloud is thought to be running on Microsoft’s full Azure service, which includes the Azure compute and controller features, as well as its SQL storage. Data on iCloud is being striped across both Amazon and Microsoft’s services, a process which allows iCloud to speed up data access since it doesn’t have to rely on a single disk or service. To accomplish this, Apple, perhaps together with Microsoft and Amazon, has come up with some sort of solution for easily identifying and accessing data across both services.