Is there a home for your data in the cloud?

A bird's-eye view of the the factors to consider. Julia King reports

Cloud storage may be creating a stir these days, but big enterprise users aren't buying in – at least not yet.

Meanwhile, vendors are in what one provider calls "education mode", explaining to CIOs, IT managers and other IT buyers they can save a lot of money by floating their data in public and private clouds.

The one thing both groups seem to agree on is that cloud storage will eventually take off. After all, it is technically feasible, it is cheaper than traditional data storage and it is becoming more and more secure.

"I look at cloud adoption a little like I look at Linux adoption 10 years ago," says John Engate, chief technology officer at San Antonio-based Rackspace Hosting. "Adoption didn't happen overnight. It came in the back door. The system administrator or developer who did work on the weekend brought in the Linux application he built and showed it around on Monday like a science project. It took a while for people to realise it's a viable way to do things."

Cloud storage is a lot further along than a science project. But is it right for part, or even all, of your organisation's data? Here are answers to five key questions that will help you decide whether you should head for the cloud.

• What is cloud storage, and how does it work?

Ask a dozen people and you'll get a dozen different definitions. In a nutshell, cloud storage is a utility-type service that provides multiple users or "tenants" access to a shared pool of storage capacity, which is accessed over an internet connection. Storage clouds are scalable, and they can easily expand or contract according to customer needs.

• What's the difference between a public cloud and a private cloud?

The public cloud is a pay-per-use storage utility. All components sit outside of the customer's firewall in a shared infrastructure that is logically partitioned, multitenant and accessed over a secure Internet connection.

Public cloud storage providers, such as with its Simple Storage Service, typically charge a monthly usage fee per gigabyte of storage plus an additional bandwidth fee for transferring data to and from the cloud. Public cloud customers require no physical storage hardware or any special inhouse technical expertise.

Rather, the cloud storage service provider manages the storage infrastructure, pooling its capacity to accommodate the needs of multiple customers. Users typically access their publicly stored data via an internet connection.

A private storage cloud is usually built behind a company's firewall, using hardware and software owned or licensed by the company. All of a company's data remains inhouse and is fully controlled by inhouse IT staffers. Those staffers can pool storage capacity to be shared across different departments or used by different project teams within the company, regardless of their physical locations.

As with public clouds, storage capacity can quickly and easily be increased by adding servers to the pool. ParaScale's Cloud Storage product and Caringo's Castor are two examples of applications that can be used to set up private cloud storage systems.

Engate describes the private cloud differentiation this way: "The user is still in the IT business, the software configuration business, the storage management and support business, and the datacentre business. You still have to have all of those resources."

There is one exception. When a private storage cloud is created by carving off a piece of a public storage cloud for one customer's exclusive use. Users pay a premium for private cloud storage, much like one pays a higher rate for a private room in a hospital.

Essentially, "the difference between public and private cloud storage comes down to the way you connect," says Mike Maxey, director of product management at ParaScale, a Cupertino, California-based vendor whose software was designed to aggregate disk storage on multiple standard Linux servers to create a single, scalable, self-managing private storage cloud.

"If you're connecting over a wide-area network and sharing the resources with other customers, it is a public cloud. This makes sense if you're a widely distributed company and creating applications, but don't have a shared infrastructure," Maxey explains. "It is also good if you're putting out transient data, like movie trailers, that might run for five months. Temporary storage in the [public] cloud makes sense."

• Is cloud storage for all types of data?

No. Cloud storage best handles large volumes of unstructured data and archival material, such as credit card and mortgage applications or medical records. For now, public clouds can't reliably handle highly transactional files or databases that require consistently fast network connections. Any kind of online transaction processing is a no-go.

Cloud storage also isn't an appropriate choice for Tier 1, Tier 2 or block-based data storage, says Jim Ziernick, president and CEO of San Diego-based Nirvanix. "If someone is trying to replace a SAN in supporting a transaction-processing system like CRM, we're not appropriate. Even if we did do block-level storage, the latency of the internet would cause a noticeable delay," he says.

"What we can do with cloud storage is give users nearly the access that they have with [network-attached storage]," he adds.

Data backup, archiving and disaster recovery are three likely uses for the cloud, says Engate.

"The cloud is for any kind of large-scale storage need with any kind of static-type data," he says. "You don't want to store a database in the cloud, but you might store a historic copy of your database in the cloud instead of storing it on very expensive SAN or NAS technology."

"A good rule of thumb is to consider cloud storage only for latency-tolerant applications," says Terri McClure, a storage analyst at Enterprise Strategy Group in Milford, Massachusetts. "Backup, archive and bulk file data would all do well in the cloud, where subsecond response time is not a requirement." On the other hand, databases and any other data that is "performance-sensitive" aren't suited for cloud storage because of latency, she notes.

But before moving any data to a cloud, public or private, users need to address a more fundamental question, says Mark Tonsetic, programme manager at The Corporate Executive Board's Infrastructure Executive Council.

"If you go to cloud storage, does it solve the problem of understanding where and why storage growth is out of control and where the point of value is [in storing a particular set of data] in the entire end-to-end business process? Just moving the technology to a cloud is not an optimal solution," Tonsetic says.

4. Who is using cloud storage today, and how are they using it?

Start-ups and new Web 2.0-based service providers, such as San Francisco-based Cloudize, are among the biggest users of cloud storage, at least for the time being. Cloudize bills itself as the first SaaS-based file collaboration tool focused on small to midsize enterprises. CEO Edwin Fu says the tool was designed to centralise all of a company's files in a cheap, scalable and collaborative way.

One of Cloudize's Web 2.0-based applications lets users of – the granddaddy of software as a service – store and share data, such as big sales presentations and video, in the public cloud. San Diego-based Nirvanix provides the public storage cloud behind Cloudize.

Fu, a former employee, describes that company's users as "low-hanging fruit" when it comes to signing up cloud storage customers. "We picked the audience because they're comfortable with SaaS and SaaS-based storage," he says. "They already have their most sensitive contact data in the cloud. What we're doing is taking the next step."

On the larger enterprise side, cloud storage customers are fewer and farther between. "We are in the very early stages of adoption. Typically, when we're talking to customers, we're talking with classic early adopters," says Nirvanix's Ziernick.

These include strictly regulated financial services companies that are required by law to store client audio conversations and other large data files, and content delivery networks that store and then stream images, audio and video to customers. More and more, users within companies are tapping cloud storage for pilot projects and proof-of-concept initiatives, Ziernick says.

Schumacher Group, an emergency medicine management and staffing company based in Lafayette, Louisiana, stores a range of documents, including contracts and reports, on's cloud platform, It also houses all accounts receivable, general ledger and accounts payable data in a hosted PeopleSoft enterprise software system, and its employee benefit information on a hosted system from Workday Inc.

"We have over 50 percent of our processes living in the cloud currently," says CIO Douglas Menefee. "All are sizable data sets with thousands of transactions being performed on a daily basis," he adds. He anticipates that by the end of this year, 75 percent of the company's processes will be in the cloud.

• Does cloud storage eliminate the need for inhouse technical resources?

Public clouds remove the need for server and storage administrators, but not all technical resource requirements go away, according to ParaScale's Maxey. Many public cloud storage services use newer protocols, such as WebDav or REST, for access, he notes. If a customer's in-house applications don't support those protocols, the technical staff will need to make changes to code. Otherwise, Maxey says, "it's like being dropped in a foreign country and not knowing the language."

Newer software applications developed in a modular fashion will be easier to adapt for storage clouds, he says; older applications will be more difficult.

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