Death of a middleman: Cloud storage gateways – and their evolution

Fading glory for Google, Microsoft and Amazon go-betweens?

For decades, we’ve survived quite nicely using on-premise storage. According to industry research, though, that may be changing as cloud-based storage emerges. A Tata Communications survey last year found that within ten years enterprises will store 58 per cent of their data in the cloud, compared with 28 per cent today.

Whether or not the shift ends up being that drastic in practice, it does seem clear that companies are getting more interested in cloud storage. Google launched a cloud storage alternative to Amazon’s Glacier and Microsoft’s Azure Backup in March, for example. Clearly, it sees an opportunity to substitute cloud storage for tape.

Whether you’re treating the cloud as an alternative to tape-based backup, or doing something more sophisticated with cloud storage, moving your data from an on-site array to the cloud isn’t always that simple.

“Cloud storage works differently than your average network-storage array, in that it is object-oriented,” points out John Sloan, research director for infrastructure at analyst firm Info-Tech Research Group.

Object-oriented storage is great for scaling out storage infrastructure, but it isn’t interoperable with the block storage typically seen on an on-site SAN. Another problem is that cloud-based storage is stateless, and typically accessed over web-friendly REST APIs. This is not the way that your legacy apps normally work.

“Also, sending and retrieving data from the cloud introduces performance hurdles (latency and bandwidth limits),” said Sloan.

Say hello to the cloud storage gateway

Cloud storage gateways are designed to solve some of these issues. They’re typically devices, whether appliances or virtual machines, that sit on the local network and pretend to be a local storage array, while interfacing with cloud-based storage.

“It is presented on the network as block or file storage, but the device is translating to objects and sending them to the cloud service,” Sloan said.

A cloud storage gateway can present cloud-based storage to a local infrastructure in an acceptable form, making it look like a filer, a block storage array, or a backup drive. In some cases, it can even present the cloud-based storage as a storage source for a local application.

“Most people are considering these gateway devices in a larger context, of solving a particular problem, so it’s part of a bigger solution,” said Randy Kerns, senior strategist and analyst at tech advisory firm Evaluator Group. “That doesn’t change the product at all, but it does change the way that it’s approached and thought of.”

“The biggest thing that an IT manager needs to understand is that there are around 17 different use cases that you can solve with gateways, and you need to be clear on how you deploy this stuff before you start asking the questions,” said Jeff Denworth, senior VP of marketing at CTERA, which makes cloud storage gateways targeting enterprise branch and remote offices.

In CTERA’s case, the cloud storage gateway doubles as a network-attached storage appliance. Customers use it as a local fileserver that interfaces into cloud environments for storage replication. It supports a variety of back-end cloud providers, having just launched a service with Deutsche Telecom.

A typical use case for a CTERA device would be to provide fast access to data locally, as you would with any local NAS device, while replicating data to the cloud in the background.

Case study

One CTERA customer, JWT, has a large presence in the Middle East, where in some regions the Internet can be slow and unreliable. During the Arab Spring uprisings, the firm had to move staff from several offices. It used a cloud storage gateway with a connection to Amazon Web Services, which enabled it to access data from the offices that were shut down.

In that way, the cloud storage gateway doubles as a backup solution, and allowed the company to save 63 per cent on its old backup system, which was tape-based. A conduit for backup and disaster recovery isn’t the only use case for a cloud storage gateway. Some vendors, like Nasuni, focus on scalability, offering what looks like a NAS but with infinite capacity thanks to cloud-based infrastructure.

Gateways can also be used for archiving in the cloud. This dovetails with automated storage tiering, in which data can be replicated between fast, local disk and cheaper cloud storage to balance space, cost, and data availability requirements.

As companies have grown to trust the cloud more, and as the logic in these devices matures, other use cases are emerging. One is collaboration, where data is replicated via a cloud storage gateway to a cloud-based storage location for incorporation into a team’s online workflow. Panzura, with its Global File System and associated controllers, is a good example of this kind of approach to cloud storage integration.

Cloud storage gateways are also useful for private or hybrid cloud scenarios. With more companies wanting the elasticity and cost benefits of cloud storage while retaining control of their data, the devices can provide a useful way to integrate legacy applications with cloud-based storage accessed over local networks, say experts. “That’s a developing area,” said Kern. Other use cases include providing an interface with cloud-based data as a primary storage mechanism, retaining little or no data on-site. That can be a dangerous approach unless you have a well-defined quality of service in your infrastructure.

“If you're using a cloud gateway and you're depending on particular performance, you have a lot of variables in there that you don't have control over,” said Kern. “Latency is a factor of environment and the risk. If you're saying ‘I need the data in a certain window’, then you have to architect the network connectivity based on that.”