Data Robotics has raised $15 million in a fourth round of funding for its consumer-focused Drobo backup storage business.

The Santa Clara, Calif., company makes “data robots,” or external backup storage units that make it easy to back up data on a computer or a network of computers. The lead investor is Greylock Partners. Other participants include new investor New Enterprise Associates, as well as existing investors RRE Ventures and Sutter Hill Ventures. To date, the company has raised $43 million in four rounds.

The company’s storage products are aimed at consumers and small businesses that don’t want to deal with technical hassles when backing up large amounts of data.

There are a host of rivals for storage inside the home or small businesses. Big companies such as Hewlett-Packard, Dell, Seagate and Netgear are diving into the networked storage market for the home. Most use a technology known as “RAID” to redundantly store data, so no data is lost even if one drive fails. But Data Robotics’ “BeyondRAID,” which uses virtualization technology to create storage that adapts to available disks. While RAID software is often complex to use and is geared toward enterprise technicians, the BeyondRAID software is simple.

Drobo holds up to four 3.5-inch hard drives. It hooks up to a Mac, Linux or Windows computer via USB port, Firewire, or gigabit ethernet wires. It shows up as a single external hard drive and doesn’t require a software installation. Unlike with RAID arrays, you can use different-size hard drives. It has green, yellow and red lights indicating how much storage is on a drive, while a blinking light is a warning not to remove a drive. You can add a drive at any time just by inserting one into a bay. Doing the same thing with a RAID array takes a lot more time. If a drive fails, you take it out and put a new one in.

To share it on a network, you simply plug it into the network via an Ethernet wire. You can then share data on the Drobo drive with other devices on the network. DroboShare can support two connected Drobos at a time, meaning the networked storage can grow to as much as 32 terabytes.

The company has sold more than 30,000 Drobo data robots in the past year, said Geoff Barrall, chief executive of the company. Many of the customers come from high-storage businesses such as video production, education, medical, photography, legal, government as well as consumers. The drives start at $499. The company was founded 3.5 years ago.

Barrall said the company will use the money to expand its sales, overseas operations and product development.