It may not seem all that exciting, but enterprise storage has investors in a tizzy. Nimble Storage, a startup that provides data storage, backup, and disaster recovery, closed an over-subscribed, mezzanine funding round of funding for $40.7 million today.

Nimble says the size of the round reflects the “rapid success” it’s been able to achieve in its 4.5 years. The company is not yet profitable, but it recently announced a massive expansion of its sales operation. It expects to IPO between the second half of next year and first half of 2014.

“It [the funding] will allow our company to invest in three key areas: continued growth and hiring, international expansion, and a strong working capital balance sheet,” said Dan Leary, VP of Marketing for Nimble Storage, in an interview with VentureBeat.

The company provides enterprise storage for customers across a variety of sectors, including eBay, Cisco, digital address book, Plaxo, Foster Pepper (a Seattle-based law firm), and the City of Cupertino. Last quarter, it added 175 new customers.

Dan Leary, the company’s VP of marketing, said that the enterprise storage space is heating up and Nimble wants to “get out well in front of this new wave.”

“Storage is sexy again,” said Leary on the topic of Dell’s $60 million fund for early-stage startups in the space. “That’s helping the visibility of the younger companies like Nimble, but with so many competing claims, you have to yell a lot louder to make sure you’re heard.”

Major competitors include Dell-owned EqualLogic, EMC, and NetApp. Pure Storage is also gaining ground with its technology that maximizes the amount of data that can be stored on solid state drives. It recently pulled in $40 million.

Above: The founding team behind Nimble Storage

Nimble Storage was founded in 2008 by Umesh Maheshwari and Varun Mehta, pictured to the left (in order) with CEO Vasuderan. Mehta was vice president of engineering at PeakStream Inc., which was later acquired by Google. Nimble Storage currently has 240 employees.

Nimble Storage targets data storage managers or IT generalists at mid-sized companies who want to combine multiple storage devices into one. It emphasizes its capability to reduce the time it takes to perform a data backup from hours or even days. They do this with a patented Cache Accelerated Sequential Layout (CASL) architecture, designed to combine flash with high capacity drives.

Today’s funding is led by the original backers from the company’s first-round, Accel Partners and Sequoia Capital. Existing investors, Lightspeed and Artis Capital participated in the round, alongside newcomer, GGV Capital.