6.033 | Preparation for MapReduce recitation

Preparation for MapReduce recitation

Read MapReduce.
Skip sections 4 and 7.

Like GFS, this paper uses the term "master", which is outdated language that the community is moving away from (see here and here for examples of alternate terms). We use the word "controller" below in place of "master", just like in GFS.

After reading through Section 3, you should be able to understand and explain Figure 1 (the "Execution overview") in detail (explaining that figure is a great test of your MapReduce knowledge, as you get ready to prepare for a future exam). After reading Sections 5 and 6, you should understand the real-world performance of MapReduce. An example question that you should be able to answer: How do stragglers effect performance?

As you read, think about the following:

MapReduce has a constrained programming model. Are the benefits of using MapReduce worth that constraint?
What types of failures does MapReduce handle, and how does it handle them?
With MapReduce and GFS, Google has made simplifying assumptions that make sense for their work and their workloads. What are the downsides of using these systems as models for reliability?

Question for Recitation

Before you come to this recitation, you'll turn in a brief answer to the following questions (really—we don't need more than a sentence or so for each question). Your TA will be in touch about exactly how to turn that in.

Your answers to these questions should be in your own words, not direct quotations from the paper.

What are the performance goals of MapReduce (both the programming model + its implementation)?
How was MapReduce implemented at Google to meet those goals?
Why was MapReduce implemented in this way?

As always, there are multiple correct answers for each of these questions.