GoGrid cost comparison with Amazon EC2
January 25, 2011 2 Comments
updated 1/30/2011 to include our own PassMark benchmark result and include GoGrid’s prepaid plan. Then updated 2/1/2011 to include cost/ECU comparison and clarifications.
Continue on our series on cost comparison between IaaS cloud providers, we will look at GoGrid’s cost structure in this post. It is easier to compare RAM and storage apple-to-apple because all cloud providers standardize on the same unit, e.g., GB. To have a meaningful comparison on CPU, we must similarly standardize on a common unit of measurement. Unfortunately, the cloud providers do not make this easy, so we have to do the conversion ourselves.
Because Amazon is a popular cloud provider, we decide to standardize on its unit of measurement — the ECU (Elastic Compute Unit). In our EC2 hardware analysis, we concluded that an ECU is equivalent to a PassMark-CPU Mark score of roughly 400. We have run the benchmark in Amazon’s N. Virginia data center on several types of instances to verify experimentally that the CPU Mark score does scale linearly as the instance’s advertised ECU rating.
All we need to do now is to figure out GoGrid’s PassMark-CPU Mark number. This is easy to do if we know the underlying hardware. Following the same methodology we used for the EC2 hardware analysis, we find that the GoGrid infrastructure consists of two types of hardware platform: one with dual-socket Intel E5520 processors, another with dual-socket Intel X5650 processors. According to PassMark-CPU mark results, we know the dual-socket E5520 has a score of 9,174 and the dual-socket X5650 has a score of 15,071. GoGrid enables hyperthreading, so the dual-socket E5520 platform has 16 cores, and the dual-socket X5650 platform has 24 cores. Hyperthreading does not really double the performance because there is still only one physical core which is hardware-threaded by two virtual cores.
Instead of relying on PassMark’s reported result, we also run the benchmark ourselves to get a true measure of performance. We run the benchmark late at night for several times to make sure that the result is stable and that we are getting the maximum CPU allowed by bursting. PassMark benchmark only runs on Windows OS, and in Windows, we can only see up to 8 cores. As a result, the 8GB(8cores) and 16GB(8cores) VMs both return a CPU mark result of roughly 7850, which is 19.5 ECU. The 4GB(4cores) VM returns a CPU mark result of roughly 3,800, which is 9.6 ECU. And, the 2GB(2cores) VM returns a CPU mark of roughly 1,900, which is 4.8 ECU. Since there are no 1GB(1core) or 0.5GB(1core) Windows VM, we project their maximum CPU power to be half of a 2-core VM at 2.4 ECU. Lastly, since we cannot measure the 16 cores performance, we use the reported E5520 benchmark result of 9174 from PassMark instead as its maximum, which is 23 ECU. These numbers determine the maximum CPU when bursting full. Based on GoGrid’s VM configuration, we can then determine the minimum guaranteed CPU from maximum CPU.
The translation from GoGrid’s CPU allocation to an equivalent ECU is shown in the following table. Each row of the table corresponds to one GoGrid’s VM configuration, where we list the amount of CPU, RAM and storage in each configuration. We also list GoGrid’s current pay-as-you-go VM price as the last column for reference.
|Min CPU (cores)||Min CPU (ECU)||Max CPU (cores)||Max CPU (ECU)||RAM (GB)||Storage (GB)||pay-as-you-go Cost (cents/hour)|
One way to compare GoGrid and EC2 is to purely look at the cost per ECU. The following table shows the cost/ECU for GoGrid VMs assuming all of them get the maximum possible CPU. We list two cost/ECU results, one based on their pay-as-you-go price of $0.19/RAM-hour, another based on their Enterprise cloud prepaid plan of $0.05/RAM-hour.
|RAM (GB)||Max CPU (ECU)||pay-as-you-go cost/ECU
In comparison, the following table shows EC2 cost/ECU for the nine different types of instances in the N. Virginia data center.
|instance||CPU (ECU)||RAM (GB)||cost/ECU (cents/ECU/hour)|
Comparing on cost/ECU only makes sense when your application is CPU bound, i.e., your memory requirement is always less than what the instance gives you.
Here, we propose a different way, comparing them by taking into account the CPU, the RAM and storage allocation altogether. Ideally, if we can derive the unit cost of each, we can straightforwardly compare. Unfortunately, GoGrid charges purely based on RAM hours, it is not possible to figure out how it values CPU, RAM and storage separately, like we have done for Amazon EC2. If we do a regression analysis, the result will show that CPU and storage cost nothing, and RAM bears all the cost.
Since we cannot compare the unit cost, we propose a different approach. Basically, we take one VM configuration from GoGrid, and try to figure out what a hypothetical instance with the exact same specification would cost in EC2 if Amazon were to offer it. We can project what EC2 would charge for such a hypothetical instance because we know EC2’s unit cost from our EC2 cost break down.
The following table shows what a VM will cost in EC2 if the same configuration is offered there, assuming we only get the minimum guaranteed CPU. Each row of the table corresponds to one GoGrid VM configuration, where we only list the RAM size for that configuration (see the previous table for a configuration’s CPU and storage size). We also show the ratio between the GoGrid pay-as-you-go price and the projected EC2 cost.
|RAM (GB)||GoGrid pay-as-you-go cost (cents/hour)||Equivalent EC2 cost (cents/hour)||GoGrid cost/hypothetical EC2 cost|
Unlike EC2, other cloud providers, including GoGrid, all allow a VM to burst beyond their minimum guaranteed capacity if there are free cycles available. The following table compares the cost under the optimistic scenario where you get the maximum CPU possible.
|RAM (GB)||GoGrid pay-as-you-go cost (cents/hour)||Equivalent EC2 cost (cents/hour)||GoGrid cost/EC2 cost|
As Paul from GoGrid pointed out, GoGrid also offers a prepaid plan that is significantly cheaper than the pay-as-you-go plan. This is different from Amazon’s reserved instance where you get a discount if you pay an up-front fee. Although cheaper, Amazon’s reserved instance pricing only applies to that one instance you reserved, and when you need to dynamically scale, you cannot benefit from the lower price. GoGrid’s prepaid plan allows you to use the discount on any instances. To see the benefits of buying bulk, we also compare EC2 cost with GoGrid’s Enterprise Cloud prepaid plan, which costs $9,999 a month, but entitles you to 200,000 RAM hours at $0.05/hour. For brevity, we do not compare with other prepaid plans, which you can easily do yourself following our methodology.
The following table shows what a VM will cost in EC2 if the same configuration is offered there, assuming we only get the minimum guaranteed CPU.
|RAM (GB)||GoGrid Enterprise cloud pre-paid cost (cents/hour)||Equivalent EC2 cost (cents/hour)||GoGrid cost/EC2 cost|
The following table compares the cost under the optimistic scenario where you get the maximum CPU possible.
|RAM (GB)||GoGrid enterprise cloud pre-paid cost (cents/hour)||Equivalent EC2 cost (cents/hour)||GoGrid cost/EC2 cost|
Under GoGrid’s pay-as-you-go plan, we can see that GoGrid is 2 to 4 times more expensive than a hypothetical instance in EC2 with an exact same specification. However, if you can buy bulk, the cost is significantly lower. The smaller 0.5GB server could be as cheap as 53% of the cost of an equivalent EC2 instance.