CS262B Reading Summary
Lessons from Giant-Scale Services
Eric A. Brewer
Summary by Feng Zhou
2/18/2004
Strong points of the paper are:
- Differenciate "yield" and "harvest" gives insight into the unique
properties of Internet services. They are both quality-of-service
metrics. But traditionally, shedding requests is the often used
method to cope with overloading. However, here the author points
out that because the properties of Internet services, in a lot of times
returning results based on partial data may be better than fulfilling
part of the requests. At least nobody sees error messages and
he/she gets some useful info.
- In general, the DQ principle is useful when designing and
provisioning a Internet service. It helps thinking about the
impact on performance and availability of various system
components, in a simple straightforward way. It also helps
planning fail-over strategies when certain components go down.
- The paper provides useful facts about giant-scale Internet
service. E.g., the peak-to-average ratio is from 1.6:1 to 6:1;
various data about several clusters used in Internet services.
One major flaw.
The DQ principle has one limitations in application. It only
applies to those services who's resource usage is roughly proportional
to the amount of data processed. In some services, the amount of
resource spent on each data item may vary greatly according to the
request type.