The costs of storage in the cloud

As part of beginning to think about the business model issues around FleSSR (one of our deliverables for next year) I've been estimating the costs of storing various amounts of data in the cloud using Amazon S3, Dropbox and Rackspace.

I've done calculations for all 3 services for between 50GB and 500PB of storage for one year.

To make the costs realistic I've had to make some working assumptions about how much data might be shipped across the network, as well as the costs for storage. On that basis, I've arrived at a total cost by starting with the costs of storage for 1 year, adding the costs of uploading all the data (spread evenly over the year) and then adding a little bit more network traffic to simulate local re-use of the data (1% per month). In the case of Amazon, where IO operations are part of the charging model, I've also had to make some assumptions about the average file size - which I've set to 1MB. So, in the case of, say, 1TB of data, I've costed the storage of 1TB in the cloud, plus the costs of uploading 93GB (1/12th of the total data plus 1%) per month, plus the costs of downloading 10GB (1% of the data) per month plus the costs of 93,000 upload operations (PUT requests) and 10,000 download operations (GET requests) per month.

Clearly the 1% figure is a complete finger-in-the-air job - I have no idea if it is reasonable or not - but I've intentionally set it quite conservatively. It is also worth noting that any scenario involving more than 500TB data storage probably has to consider how the data is uploaded to the cloud in the first place (other than by using the network), so my calculations probably go a bit wrong in those cases.

My costings come out higher than similar estimates that I've seen from other sources... I think because people tend not to include the costs of transferring data across the network when they do this kind of thing. Network costs are actually quite significant in terms of the overall price.

Prices are based on the available information on the web (Amazon S3, Dropbox, Rackspace). Note that Rackspace's pricing includes support and a Content Delivery Network (CDN) and so isn't directly comparable with Amazon S3. Also that the largest offer from Dropbox is for 100GB of storage, so that service isn't relevant for most of my data points.

A Google spreadsheet of my workings is available. Please let me know if you think I've made any mistakes.

The point here is not to make comparisons between these three services - please don't use my numbers to do that. Indeed, making such a comparison based only on cost would be rather foolish because there are significant differences between the services in other ways. Rather, it is just to get a feel for how the different charging models work and, more importantly, to get a feel for what we are up against as we think about transforming FleSSR into a production service.

So, what can we conclude? Looking at the cost per TB per year, the Dropbox and Rackspace prices are pretty much flat (i.e. the same irrespective of how much data is being stored) at around £1530/TB/year and £1220/TB/year respectively (though, as noted above, the Dropbox prices are only applicable for 50GB and 100GB). Amazon's pricing is cheaper, particularly so for large amounts of data (anything over 100TB data where the price starts dipping below £1000/TB/year) but never reaches the kind of baseline figures I've seen others quote for Amazon storage alone (i.e. without network costs) of around £450/TB/year. (My lowest estimate is around £510/TB/year for 500PB data but, as mentioned above, this estimate is probably unrealistic for other reasons.)

Superficially, these prices seem quite high - they are certainly higher than I was expecting. What is interesting is whether they can be matched or beaten by academic providers (such as Eduserv) and/or in-house institutional provision, and if so by how much?

I'll return to that question in a later post.