Today there’s no easy way to escape your cloud provider. Some firms are trying to fix that. All the major cloud providers use technology different enough so that switching from one to another would require customers to rewrite much of their software. Still, in the next five years about one-third of companies using the cloud may either switch providers to get a lower price, or add another provider to get servers closer to customers or have a backup should one company suffer a meltdown. That’s why last year’s top story in the $57-billion public cloud market was the rise of so-called container software such as Docker, which chops up and isolates apps to make transitions easier.