After a beta period stretching nearly 15 months, Amazon Web Services today made its Elastic File System (EFS) generally available. The service is not without limitations: it’s available only for Linux, in only three of AWS’s 13 cloud regions worldwide, and it’s expensive.

But the new technology is significant because much of the world’s information technology relies on file systems, yet until now AWS hasn’t offered any that are truly scalable, one storage executive said. EFS is also the first among AWS’s several storage systems to work with multiple Elastic Compute Cloud (EC2) instances, Amazon said in an online FAQ, thus filing a gap in AWS’s offerings.

“This is Amazon making one more step toward real-world IT, because there are a huge number of applications that were written for a file system as opposed to object storage,” said Jerome Lecat, CEO of San Francisco-based storage firm Scality. “The reality of today is file systems, and we need to be able to on-ramp those into modern storage technology.”

File systems, which organize and track files for storage and retrieval, allow locking some files and giving different users varying permissions. Until now, they have been difficult to scale above a few hundred thousand files, Lecat said. In contrast, object storage can accommodate billions of files, but it lacks those tracking and control capabilities, and older applications must be rewritten to use it — a non-trivial task, he said.

EFS supports only Linux-based instances, which disappointed Kevin Felichko, CTO of PropertyRoom.com, an online-auction company in Frederick, Md. His company has numerous Windows-based EC2 instances.

“We’ve been waiting for EFS, and now that it’s been released, having that limitation is a bummer, because we’d love to use it,” Felichko said. He said he hopes and presumes Windows support will be forthcoming.

EFS makes it simple to set up and scale file storage in the AWS cloud, Amazon said in today’s announcement. By pointing and clicking in the AWS Management Console — or through the command line or an API — customers can use EFS to create file systems that are accessible to multiple Elastic Compute Cloud (EC2) instances simultaneously via the Network File System (NFS) protocol, it said.

As the name implies, EFS automatically scales customers’ storage to fit their files. File systems up to petabytes in size can be accommodated. EFS also automatically scales throughput and input/output operations per second (IOPS) to match a customer’s performance needs. Every file system can burst to at least 100 MB per second, AWS said, and those greater than 1 TB can burst to higher throughput as file system capacity grows

It’s no wonder the beta lasted so long, Lecat said. “What AWS did is very difficult. Making a really scalable file system requires a completely different design.”

EFS redundantly stores each file system across multiple availability zones, reducing odds of failure. It can be used for a variety of throughput-heavy workloads, including big data, analytics, media processing, content management and web serving.

EWS is an alternative to Elastic Block Storage (EBS), which AWS said offers low-latency access, but only to data from a single EC2 instance. It’s also an alternative to the widely used Simple Storage Service (S3), intended for object storage, and to Glacier, which is intended for archival storage.

Amazon announced EFS at its AWS Summit in San Francisco in April 2015. In June 2015, It said EFS would become available in the U.S. East (northern Virginia) and E.U. (Ireland) regions within two months, according to a TechTarget report.

EFS is immediately available in the U.S. East (northern Virginia), U.S. West (Oregon), and E.U. (Ireland) regions. AWS said it will expand to additional regions “in the coming months,” but didn’t provide details. It costs 30 cents per GB per month, though customers within their first year on AWS get up to five GB per month free.

“That is expensive enough so that companies with a lot of data — say, a petabyte or more — may opt to stay on-premises,” Lecat observed.