Before the release of EBS, storage in an EC2 instance was deleted the second that instance shut down, unless the EC2 user had created a manual workaround to tie EC2 to Amazon's Simple Storage Service (S3). That meant that hardware failures caused data loss, and people couldn't scale down their EC2 usage temporarily for risk of losing data or increase use greatly because of storage limitations.
Now, however, users can mount a persistent virtual storage "device" that acts much like an unformatted hard drive and then create a file system on top of it or use it as raw, unstructured storage that runs independently but related to EC2 instances. "As an EC2 instance is to a traditional server, an EBS instance is to a traditional disk," Adam Selipsky, VP of product management and developer relations for Amazon Web Services. Users can store up to 1 TB of data in a single instance of EBS and can scale to as many EBS instances as they need.
The new feature also instantly makes EC2 more reliable, since the storage is now decoupled from the computing resources and is automatically replicated to prevent data loss if hardware fails. Amazon estimates EBS volumes will be 10 times more reliable than commodity hard drives.
Customers will likely use EBS for a variety of things, including as a cloud-based database for an app running on EC2, storage area networking as a service via EBS' distributed file system possibilities, a reliable test bed for Web applications, and Web hosting. In an early example, developer Eric Hammond has created a guide for those looking to run MySQL on Amazon EC2. Applications like that could make corporations take a harder look at the service for business use.
Among those testing EBS are Wired.com/CondeNet, which uses EC2 to host embeddable widgets and Wired product reviews.
"EBS is the missing link -- the last piece in the cloud computing puzzle -- that enables start-ups and large corporations alike to conjure the resources they need to build any application possible," Paul Fisher, manager of technology for Wired.com/CondeNet, said in a statement. "Persistence is key to most applications, and EBS provides more flexibility in this area than anything previously available."
However, despite making data more reliable and EC2 more flexible, EBS does nothing to quell concerns over Amazon's Web services' availability. Last month, Amazon S3 was down for most of a day, forcing the company to offer refunds for breaking service level agreements that require the services to be up and accessible.
In a blog post, Amazon CTO Werner Vogels said the company sees the possibility of customers using EBS and S3 in tandem for storage management because of a feature that allows users to create snapshots of data at a certain point in time, store them in S3 and then use them for back-up and rolling back data to previous versions.
Amazon claims EBS will also be faster than the previous "ephemeral" EC2 storage, with lower latency and better throughput. EBS may be cheaper for some, too. It costs 10 cents per GB per month and 10 cents per million requests for a file or data. In an example presented on Amazon's site, a Website that has a 100 GB database and averages 100 I/Os per second during a month would spend only $10 monthly on storage and $26 monthly in throughput costs. Previously, developers also had to pay for a whole EC2 instance and all the storage that went with it, rather than a small amount of storage if, say, they only required a 10 GB database.
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