Cloud Block Storage: Building with the Blocks that Perform

cloud building blocks By Sue Poremba

Block storage itself is a very old idea. Hard drives (and other storage media) present themselves to operating systems as a collection of blocks, each of which store data. The operating system is responsible for turning those blocks into something that applications can use. So when people say “block storage,” what they’re really talking about is storage that behaves like a hard drive.

“Cloud block storage is block storage that’s been built to integrate with cloud platforms. Usually cloud block storage is distributed across many computers and many hard drives,” explained Ross Turk, the VP of Community at Inktank, the commercial support company behind the open source storage project, Ceph.

Elastic Or On Demand

Cloud block storage caters to the need for enterprise-class applications running in the cloud, said Felix Xavier, CTO of CloudByte. According to Xavier, some of the features that define cloud block storage include the following:

  • It should be elastic or on-demand, in terms of storage capacity and performance.
  • Need to provide the mechanism to migrate the chunk of storage, also known as logical unit number (LUN), from one node to another participating node seamlessly.
  • Each LUN should have should have guaranteed Quality of Service (QOS) in terms of Input/Output Operations Per Second (IOPS), latency and throughput.
  • Need to have single console management and monitoring for complete storage infrastructure where storage nodes are spread across multiple data centers.
  • Need to have delegated admin capability where client admins can manage their own chunk of storage in terms of snapshot, replication, etc.
  • It should be reliable highly available. A 2-3-node failure should not impact anything running on the storage infrastructure.
  • Each LUN should have disaster recovery parameters such as replication interval, location, etc.

Resilient, Scalable, Flexible

That cloud block storage is more resilient, more scalable, and more flexible makes it advantageous to a business’s computing plan. “Because cloud block storage scales the same way the cloud does – out, instead of up – it doesn’t have the limitations typical of block storage solutions that weren’t designed with the cloud in mind,” said Turk.

Other key benefits, Xavier added, are the on-demand storage provisioning in terms of capacity and performance, the ability to buy storage capacity and performance independently, and applications requiring dedicated storage infrastructure can be hosted in the cloud.

Before Cloud Block Storage

Before cloud block storage, you couldn’t simply purchase more hard drive space. Instead, when you ran out of room, you had to purchase an entire new cloud server. Now, those who need more storage space can turn to cloud block storage that can, for instance, be used in Rackspace’s Cloud Server powered by OpenStack.

The option you decide to choose for your cloud block storage will depend on your overall needs, as Chuck Their pointed out. “Standard drives are the go-to option to for users who simply need to increase their hard drive size with extra storage to store things like logs, backups or images for your website,” he wrote. Users who have high performance needs would want to consider a Solid State Drive. And there are also hybrid options available.


Who should consider cloud block storage is a much easier question to answer, however. “With block based storage it’s not as much about industries as it is about applications or usage scenarios, also preferences of those using it,” said Greg Schulz, senior advisory analyst with the StorageIO Group. “For example, some applications want to see or expect block-based storage such as older backup/restore or archiving tools, or some databases. In some scenarios, block can also be faster than file-based access, so if a cloud block storage is engineered and deployed correctly, that might be more robust than object or other access. Thus for database or other applications, block cloud storage can be a good thing for some users.”

“Anyone who runs a cloud platform needs cloud block storage,” Turk added. “Virtual machines cannot run without it. However, there are a lot of choices that can be made regarding cloud block storage solutions. Price, flexibility, and overhead are all factors that should be considered.”

This article originally appeared in my previous Web2 and More blog.  Author bio: Sue Poremba is a freelance writer focusing primarily on security and technology issues and occasionally blogs for cloud service provider Rackspace Hosting.