A storage startup called Nasuni is unveiling a virtual NAS file server that runs on VMware and connects customers to cloud platforms such as Amazon's Simple Storage Service, adding encryption to enhance security and several features to improve performance.

Nasuni was founded last year and on Tuesday is announcing the beta version of its Nasuni Filer – a so-called "cloud storage gateway." Target customers are mid-sized companies who are interested in cloud storage, but are concerned about exposing sensitive data or suffering from high latency.

"We connect our customers to partners, people like Iron Mountain and Amazon that provide cloud storage, and we are delivering it as a file server in your virtual environment," says Nasuni founder and CEO Andres

Rodriguez, who previously founded Archivas, an online storage management software vendor acquired by Hitachi Data Systems three years ago. 

Nasuni is based in Natick, Mass., with 18 employees, and has $8 million in first-round funding from North Bridge Venture Partners and Sigma Partners. Rodriguez says Nasuni has eight customers in alpha mode and is now offering the filer in a free public beta.

Nasuni's NAS file server runs in a VMware virtual machine and integrates with either Amazon S3 or Iron Mountain remote storage services, while providing features such as encryption, caching, deduplication, automatic provisioning, and synchronous snapshots.

Accessing cloud storage introduces latency, Rodriguez says, but Nasuni allows users to work with a local cache, speeding up access to data.

"It's quite clever," says IDC analyst Laura DuBois. "It does address security concerns in the form of encryption of data in flight and at rest, and it also certainly addresses the concerns around availability."

Nasuni is one of many startups building software and services that add capability to cloud platforms such as Amazon. For example, the company RightScale was founded to help customers build and clone virtual servers and manage storage in the cloud, and Symantec offers storage management for Amazon customers.

Nasuni will make its product generally available in the spring, and add more partners before doing so, according to Rodriguez. Nasuni will start charging customers after the beta trial, with fees starting around $250 a month. Although two vendors will be involved in each sale, customers would receive just one bill, which could come either from Nasuni or a partner depending on the billing model, he says.