As I discussed in my previous post, What Makes Cloud Storage Different from Traditional SAN and NAS?, today's cloud storage is unique from the SAN and NAS (and even CAS) that has gone before. Beyond the cost and flexibility benefits inherent in public cloud computing resources of all sorts, cloud storage is unique in its openness, programmability, and the possibilities it opens for distribution and collaboration.
These compelling benefits, along with an explosion of cloud hype, have led every company with a product even remotely "cloudy" to jump into the market. In my corner of the IT world, everyone from hosting providers to software vendors to traditional array manufacturers are putting forth cloud storage products. As the wise among us already know, these cloud products are not all of equal merit!
It has struck me that there are really three kinds of cloud storage offerings today: Storage in the cloud, cloudy storage systems, and full-on cloud storage. Each will likely find its own niche within the overall IT infrastructure landscape, but buyers should be careful when comparing these solutions!
| | Cloud Storage | Cloudy Storage Systems | Storage in the Cloud |
| Commonly called |
Public cloud storage |
Private cloud storage |
Hosted storage |
| Example |
Nirvanix
Amazon S3 |
EMC Atmos
Cleversafe |
Amazon EBS
Flexiscale storage |
| Capacity Granularity |
Per-object
e.g. $.25/GB/month |
Per-system
e.g. $150,000 for 120 TB |
Standard config
e.g. 20 GB per instance |
| Protocol |
API* |
API, file |
file, block |
| Access Method |
object/
metadata |
object/
file |
file/
block |
| Connectivity |
Internet |
WAN/
LAN |
LAN/
SAN |
| Optimized for |
Collaboration
Flexibility
Scalability |
Flexibility
Scalability |
Familiarity
Performance |
| Use case |
Offsite storage
Collaboration |
Unstructured data |
Web applications |
* Note that Nirvanix offers CloudNAS, a standard POSIX filesystem interface
Most of the current cloud storage offerings jostling for position in the marketplace fit into one of the categories above, but of course the picture isn't so neat in reality. Some Nirvanix customers, for example, connect to the service through a private WAN or even LAN connection. But these categories can help to cut through the marketing hype and understand just what is being offered by a vendor.
One particularly important factor is what I'm calling capacity granularity, which is the basic amount of storage you get and how you pay for it.
Consider the diagram above, which shows storage of each of the three types used for a steadily-growing application:
- If you're relying on hosted storage in the cloud, you probably can't scale like this at all. Your server instance comes with some amount of storage (perhaps 20 GB) and that's all you get. Maybe you can buy another 20 GB or upgrade the server, but flexible scaling isn't the intended purpose of this type of storage.
- If you deploy your own private cloud, you have to buy some large amount of capacity just to get started, perhaps as much as 120 TB. You then spend the next year filling this capacity up until you need to buy another of these large systems. This model should sound very familiar to anyone who has bought enterprise storage over the last decade!
- True cloud storage grows with you. You pay for used capacity and can scale as your usage grows. Although smaller organizations like to pay monthly as they grow, large enterprises often negotiate a regular monthly payment. Either way, though, they only pay for what they use!
Which cloud storage model fits your needs?