Thanks to the cache speed of access it is similar to if you had a traditional local primary storage device. Since you are only keeping active data local you can justify spending more on the device that serves as this cache too. For example we are running our test scenario on an SSD equipped server. All of our active data can be served at SSD speeds. The cache is an essential ingredient to these solutions. It provides you with access to your data in case your connection to the cloud or the cloud provider has an issue. Although in our lab we have lost our internet connection only once in the last three years it is something that IT professionals always worry about, the cache insulates you from the potential connectivity loss.
In this scenario backups may become a thing of the past. As stated above, changes to the data is snapshotted and replicated in either real time or near real time to the cloud provider of your choice. In some cases the software can be configured to send the data to two separate cloud providers for even more redundancy. Those snapshots can be retained for as long as you see fit. Obviously the monthly cost from the cloud provider will increase as the data they store for you grows.
With data being continuously replicated to the cloud as it changes you can get to any version of a file for as long as you have the retention policy set. You'll want to explore the products, most are available as a free trial, to make sure that you are comfortable with the way recovery of a file from a snapshot works as well as how long it takes to perform that recovery.
The Achilles heal for cloud based backup solutions has always been a full system or data center recovery. Transferring all the data across the internet that a server needs is a challenge. Cloud as primary storage circumvents this problem because your data is where it supposed to be, in the cloud, In a full server recovery the only thing that needs to be transferred back is enough information to populate the cache and that should be able to be done as data is being accessed not all at once.
A NAS service that is cloud enabled works well in this scenario. If the server hosting the cache or the cache itself fails, re-download the NAS software and let cache begin to repopulate as files are accessed. Block based storage that is cloud enabled may require more thought. Ideally keep the boot drive as small as possible and do an image backup of it, which if this is a virtual server, you may already have. Then upload the image to the cloud and you have the same accessibility and recovery situation as the NAS service does.
Is cloud as primary storage for everyone? No, but that does not mean that these solutions are only for small businesses either. As the software and the providers continue to mature the scope of use cases that they can encompass will expand. The advantage cloud enabled primary storage has is that it is very easy to test. You can test a 10TB configuration without installing 10TB of storage.
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George Crump is lead analyst of Storage Switzerland, an IT analyst firm focused on the storage and virtualization segments. Find Storage Switzerland's disclosure statement here.