The choices you make when selecting a cloud storage provider depend in large part on your environment and what you are trying to accomplish. A small business may be looking to the cloud to start an IT service like file sharing, a larger business may look to the cloud to augment an existing process like backup. Despite those differences everyone should look for security, availability, and flexibility. In the first entry in this series we will discuss security.

As we discuss in "What is Cloud Storage," cloud storage providers (CSP) come in two forms typically. There are providers that provide a complete turnkey system, where they provide an application that moves data to the cloud and they manage and provide the physical storage assets in the cloud.

Then there are the providers of just the physical storage assets in the cloud that you either directly connect to or you connect through a third-party software application or hardware appliance. In that case the choice is typically yours for which cloud provider you will connect to.

There are some third-party software applications that only work with a single cloud storage asset provider. In other words they look like a turnkey solution but are outsourcing the backend storage themselves.

None of these CSP methods is better than the others. Choosing which one makes the most sense for your organization depends on your needs and each of these CSPs can deliver on security, availability, and flexibility.

Security, as we discussed in "Consumer Cloud vs. Enterprise Cloud," is certainly critical for any size of organization and many users of cloud storage. Encryption of some type is typically the security solution, but it is the where and when of that encryption that becomes important. At a minimum you want your data that is at rest in the cloud to be encrypted. The primary motivation is to make sure that, if the CSP hosting your data is responding to a legal action and needs to provide access to data, your data can't be read.

Storing encrypted data at someone else's facility and then having that facility come under investigation is going to make for some very interesting legal arguments and is something I am going to cover in a future entry. In short, while encryption alone does not free you from a court order, it at least gives you the control over who will and will not see your data.

Beyond encryption at the facility, most businesses will also want to consider having that data encrypted as it is being transferred to the remote cloud storage, known as encrypting on the wire. This can be done by the software or hardware that is connecting you to the cloud. Encryption is not free though; it may come at the expense of a small performance loss, especially if transfer is being done by a software-based application. For most, this loss should be well worth the gain in security.

Most cloud storage applications use local storage to cache data as it moves back and forth between the CSP. This local storage should be encrypted, too. Local encryption protects you if a hard drive needs to be disposed of. Unlike a RAID system, although it is still readable, it requires some effort to read data from discarded drives. Most of these caches can exist on a single hard drive, and without encryption they would be very easy to read. By simply removing the key they are rendered useless.

Next up in this series is availability. The spring was a tough time for cloud storage providers with several major names exiting the market and several well-publicized outages, from companies like Amazon and VMware. The focus of that entry will be selecting a provider that has minimal chance of an outage and what to do if there is one.

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George Crump is lead analyst of Storage Switzerland, an IT analyst firm focused on the storage and virtualization segments. Storage Switzerland's disclosure statement.

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