Accumulo

Chapter 13. Performance

One aspect of working with big data is the chance to regularly exercise computer science performance theory. Desktop computers are so powerful that sometimes application developers can get away with inefficient designs without affecting performance to the extent that users notice. When you work with many terabytes of data, performance and efficient design once again become paramount.

Scalable applications that interact with large numbers of users often need to respond to requests very quickly, in under a second. Jakob Nielsen suggests acknowledging time limits that affect how users perceive an application:¹

0.1 second is about the limit for having the user feel that the system is reacting instantaneously, meaning that no special feedback is necessary except to display the result.

1.0 second is about the limit for the user’s flow of thought to stay uninterrupted, even though the user will notice the delay. Normally, no special feedback is necessary during delays of more than 0.1 but less than 1.0 second, but the user does lose the feeling of operating directly on the data.

10 seconds is about the limit for keeping the user’s attention focused on the dialogue. For longer delays, users will want to perform other tasks while waiting for the computer to finish, so they should be given feedback indicating when the computer expects to be done. Feedback during the delay is especially important if the response time is likely to be highly variable, since users will ...