Thesis Document Finished

After a week of fun and networking in northern California earlier this month, where I attended Google IO, I came back with renewed energy to finish the writing process on my thesis document. I'm proud to present it here:

Recent EC2 related events and thesis update

I continue writing my thesis document, chapter 4 is finally taking form and will be finished this week. Then I first need to make a couple of additions and changes to my broker prototype, before I can start writing my final 5th chapter that handles about the evaluation of the performance (in terms of the achieved cost reduction) of my proposed broker. Will try my best to finish a draft before next Friday (May 6th) when I leave for San Fransisco to attend the Google IO conference.

Recently a couple of interesting EC2 related events happened.

With headlines as "Amazon Gets A Black Eye In The Cloud With Server Crash", "Amazon outage casts a cloud over cloud computing?", "Amazon’s EC2 Outage Proves Cloud Failure Recovery is a Myth!" and "Lessons From a Cloud Failure: It’s Not Amazon, It’s You". They all refer to the failures that began Thursday morning (US time) as the Amazon Cloud Crash. These failures were caused because of RDS databases that started to backup theirselves and connectivity problems in multiple availability zones in the US-East region. Popular websites such as Quara, Reddit, GroupMe and FourSquare were affected and weren't reachable for hours. Customers should foresee failure scenarios and do not rely on instances of single cloud provider in a single regions ... as always a single point of failure should be avoided. That's why AWS explicitly advises their developers to design their site’s architecture so that it is resilient to occasional failures and outages. This event brought cloud computing in the picture rather negatively, today the AWS website or AWS blog do not contain any articles telling their users what caused the outages. During the outages there was however a little update every hour or so on the AWS Health Dashboard, we see there that the recovery to bring everything back to normal took about 4 days.
Note: on Rightscale a good blogpost was found about the EC2 US-East outage.

On a different note on April 22th, AWS posted the public IP ranges used by the different geographical EC2 regions, accompanied by this introduction:

We are pleased to announce that as part of our ongoing expansion, we have added a new public IP range (APAC-Tokyo).

These IP ranges can be found here. They can be seen as an indication of the size of the different EC2 regions, it's interesting to have a look at how these number of IP addresses relate to each other:

From this data we see that more than half of all the public IP addresses provided by Amazon EC2 are situated in the US-East region, it is followed by EU-West and US-West who account for about 15 percent of the IP addresses. The Asian regions only represent less than 10 percent of the IP addresses, but these regions are the newest introduced regions and are possibly growing faster than the other regions.

Amazon EC2 News (ctd)

On Novemer 15th Amazon EC2 once again had an EC2 related announcement to make: a new instance type, called "Cluster GPU Instance". The incentive to launch this instance type according to Amazon: "GPUs are increasingly being used to accelerate the performance of many general purpose computing problems. However, for many organizations, GPU processing has been out of reach due to the unique infrastructural challenges and high cost of the technology". For the moment this instance type is only available in the US East (N.Virginia) region (with Unix/Linux) as on-demand and reserved instances. The on-demand version is priced 2.10 dollar per hour, while the reserved instance has a 1-year fixed price of 5630 dollar and a hourly rate of 0.74 dollar. Some further reading can be done on the following locations:

• This article on Werner Vogels blog gives a good overview of the incredible power of these instances (over a TeraFlop per instance).
• Amazon makes it possible for anyone to use a supercomputer by offering it on-demand, but is it performance the same as with in-house hardware? It seems to be according to these benchmarks.
• Nvidea explains its architecture and what makes GPU computing so attractive here.
• In the official press release some applications that could benefit from this instance type were already mentioned: medical imaging visualization software, financial data analysis and simulation, rendering of sophisticated CGI,...

Amazon Spot Instance Pricing [CloudExchange.org]

After getting some advice, I made some new graphs from the cloudexchange input data that:

• plots the average spot price for each day of the week (for every instance type)
• plots the average spot price during each hour of the day (for every instance type)

A first example of this new output for a us-east-1.linux.c1.xlarge spot instance:





And as a second example the output for a us-east-1.linux.m1.xlarge spot instance:





We notice that some spot instances have a rather fluctuating price during the day and over the days of the week, while others do not show this behavior. This updated version of the software can be found here. And all the generated graphs can be downloaded from this location.

Afterwards I made a little program that takes the CSV files found on cloudexchange.org as input and calculates what the average spot instance price has been between two given dates for each instance type. This program can be downloaded here. The output is written to a new CSV file, for the Linux instances a PDF version of this file can be found here.

Reserved vs On-Demand Instances

On Amazon EC2 these terms have the following meaning:

• Reserved instances:

  They give you the option to make a low, one-time payment for each instance you want to reserve and in turn receive a significant discount on the hourly usage charge for that instance.

• On-Demand instances:

  They let you pay for compute capacity by the hour with no long-term commitments. This frees you from the costs and complexities of planning, purchasing, and maintaining hardware and transforms what are commonly large fixed costs into much smaller variable costs.

I had a look today at the problem of finding the optimal division between Reserved and On-Demand instances. With the optimal solution being the one with the smallest total cost. My findings (in an Excel file) can be found here. Or I put them in two pdf files as well:

• General Pricing Information: download here
• Practical Example: download here

Amazon Spot Instances Pricing [CloudExchange.org]

On cloudexchange.org we find the history of the price of the different Amazon Spot instances, this data is exporteable as an CVS file.
I made a little Java program (download here) that takes this file as input and generates the following graphs:

• one containing the average price for the spot instance during each day


• one with a line representing the average price during the day and a line for the average price during the night (0:00-8:00AM)

On the following graph we notice that for the corresponding spot instance (us-east-1.linux.m2.4xlarge) the average day price does not have peaks during the weekends (2 units on the rights of every vertical grid line), which seems logical.


For the same instance I then divided this graph in the day and night parts, but it seems there is no remarkable difference in price.


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Papers

I read these 3 papers during the weekend:

1. "Exploiting Non-Dedicated Resources for Cloud Computing" by Andrzejak A., Kondo D. and Anderson D.P.:

   ABSTRACT Popular web services and applications such as Google Apps, DropBox, and Go.Pc introduce a wasteful imbalance of processing resources. Each host operated by a provider serves hundreds to thousands of users, treating their PCs as thin clients. Tapping the processing, storage and networking capacities of these non-dedicated resources promises to reduce the size of required hardware basis significantly. Consequently, it presents a noteworthy opportunity for service providers and operators of cloud computing infrastructures. We investigate how a mixture of dedicated (and so highly available) hosts and non-dedicated (and so highly volatile) hosts can be used to provision a processing tier of a large-scale web service. We discuss an operational model which guarantees long-term availability despite of host churn, and study multiple aspects necessary to implement it. These include: ranking of non-dedicated hosts according to their long-term availability behavior, short-term availability modeling of these hosts, and simulation of migration and group availability levels using real-world availability data from 10,000 non-dedicated hosts. We also study the tradeoff between a larger share of dedicated hosts vs. higher migration rate in terms of costs and SLA objectives. This yields an optimization approach where a service provider can find a suitable balance between costs and service quality. The experimental results show that it is possible to achieve a wide spectrum of such modes, ranging from 3.6 USD/hour to 5 USD/hour for a group of at least 50 hosts available with probability greater than 0.90.

2. "Reducing Costs of Spot Instances via Checkpointing in the Amazon Elastic Compute Cloud" by Andrzejak A., Kondo D. and Yi S.:

   ABSTRACT Recently introduced spot instances in the Amazon Elastic Compute Cloud (EC2) offer lower resource costs in exchange for reduced reliability; these instances can be revoked abruptly due to price and demand fluctuations. Mechanisms and tools that deal with the cost-reliability trade-offs under this schema are of great value for users seeking to lessen their costs while maintaining high reliability. We study how one such a mechanism, namely check pointing, can be used to minimize the cost and volatility of resource provisioning. Based on the real price history of EC2 spot instances, we compare several adaptive check pointing schemes in terms of monetary costs and improvement of job completion times. Trace-based simulations show that our approach can reduce significantly both price and the task completion times.

3. "Decision Model for Cloud Computing under SLA Constraints" by Andrzejak A., Kondo D. and Yi S.:

   ABSTRACT With the recent introduction of Spot Instances in the Amazon Elastic Compute Cloud (EC2), users can bid for resources and thus control the balance of reliability versus monetary costs. A critical challenge is to determine bid prices that minimize monetary costs for a user while meeting Service Level Agreement (SLA) constraints (for example, sufficient resource availability to complete a computation within a desired deadline). We propose a probabilistic model for the optimization of monetary costs, performance, and reliability, given user and application requirements and dynamic conditions. Using real instance price traces and workload models, we evaluate our model and demonstrate how users should bid optimally on Spot Instances to reach different objectives with desired levels of confidence.

It took a while (I read some parts more than 3 times) to understand everything the papers were talking about, but now I think I get what they are saying. And the presented models sure will be a good extension to the model I'm creating.

Cloud Computing General [A]

This week I did a few general things to get in a cloud computing mood again:

1. On Monday September 27th I attended the Microsoft conference 'A Journey to the Cloud' (http://msdn.microsoft.com/nl-be/ff955851.aspx), where I went to the following talks:
   
   
   
   • The Microsoft Cloud Continuum (Bart Vande Ghinste, Enterprise Architect for MS Belgium & Luxembourg): this was a good summary of what cloud computing stands for and why MS beliefs it will be big.
   
   
   • The Road to a Private Cloud Infrastructure (Eduardo Kassner, Enterprise Technical Architect for MS Corporation): this was less interesting, because the talk was very Microsoft oriented and the recorded demo videos were hard to follow for someone who has no Windows Azure experience.
   
   
   • An Architecture Lap around the Windows Azure Platform (Kurt Claeys, Technical Solution Specialist for MS EMEA): fun introduction to the Azure platform.
   
   
   • IaaS: Principles and Patterns for the Private Cloud (Alberto Boczar, Technical Architect for MS Corporation): this was a very good speaker which made his talk interesting. He presented a general overview of the principles and patterns of cloud computing.


2. Started reading "The Big Switch: Rewiring the World from Edison to Google" by Nicholas Carr on my Kindle. (http://goo.gl/GBBu)


3. I experimented a bit with Amazon EC2. Became a bit familiar with the AWS Management Console interface, ran an instance for the first time and connected to it through SSH, ...