My previous posts have described the costs of running data applications on the cloud. In this post, I provide a simple example of a cost-effectiveness study to answer the question: Is it cheaper to host an on-demand image mosaic service locally or on the Amazon EC2 cloud? The costs described here are current as of October 2010. See Berriman et al. (2010) for a full description.
The cost calculations presented assume that the two services process requests for 36,000 mosaics of 2MASS images (total size 10TB) of size 4 sq deg over a period of three years. This workload is typical of the requests made to an existing image mosaic service hosted at the Infrared Processing and Analysis Center (http://hachi.ipac.caltech.edu:8080/montage/). We assume that the processing is done on 2.66 GHz dual core Xeon processors with 2 GB memory (designated c1.medium by Amazon) or equivalent machines. These are the most cost-effective Amazon machines for running Montage (see What Types of Science Applications Are Best Run On The Cloud?).
Table I summarizes the costs of the local service, using hardware choices typical of those used at my home institution, the Infrared Processing and Analysis Center (IPAC) at Caltech. The roll-up of the power, cooling and administration are estimates provided by IPAC system management. Table II gives similar calculations for Amazon EC2; the costs there include the costs of data transfer, I/O etc. Clearly, the local service is the least expensive choice. The high costs of data storage in Amazon EC2, and the high cost of data transfer and I/O in the case of an I/O-bound application like Montage, make Amazon EC2 much less attractive than a local service.
The results indicate that for an I/O bound application, which are common in astronomy, the high data storage costs and the high I/O and transfer-out costs may make Amazon EC2 less attractive than a locally hosted application in this example. Now, this does not mean that Amazon EC2 is a poor choice in general. Amazon would, for instance, become more cost effective as the load on the service declines. In a future post, I will describe how a processing bound astronomy application can be much more cost effective to run on Amazon than on a local machine.
TABLE I. COST PER MOSAIC OF A LOCALLY HOSTED IMAGE MOSAIC SERVICE
|12 TB RAID 5 disk farm and enclosure ( 3 yr support)||12,000|
|Dell 2650 Xeon quad–core processor, 1 TB staging area||5,000|
|Power, cooling and administration||6,000|
|Total 3-year Cost||23,000|
|Cost per mosaic||0.64|
TABLE II. COST PER MOSAIC OF A MOSAIC SERVICE HOSTED IN THE AMAZON EC2 CLOUD
|Network Transfer In||1,000|
|Data Storage on Elastic Block Storage||36,000|
|Processor Cost (c1.medium)||4,500|
|Network Transfer Out||4,200|
|Total 3-year Cost||52,700|
|Cost per mosaic||1.46|