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In the cloud, which of the following is the main purpose of placing web servers and database replicas across several availability zones within the same region?

  1. ATo keep the service running in other zones even when a failure on the scale of a single data center (such as a power or cooling failure) occurs
  2. BTo place servers in various parts of the world so that responses come from places near users, reducing communication latency
  3. CBecause communication between zones has no latency and no charge, making processing faster and cheaper than in a single zone
Show answer and explanation

Answer: A. To keep the service running in other zones even when a failure on the scale of a single data center (such as a power or cooling failure) occurs

A region is a geographic area where a cloud provider has data centers, and an availability zone within it is a group of one or more data centers whose power, cooling and networking are independent of the other zones. Zones are connected by low-latency links, so placing servers and data replicas across several zones lets the service continue in the remaining zones if one zone stops. To prepare for disasters that affect a whole area, replicas are also placed in another region. Communication between zones does have latency and may be charged, so the design must take the data replication method into account.

  • A. Correct. Zones have independent power and networking, so the system can survive the failure of one zone.
  • B. Responding from places near users is the purpose of using several regions or a CDN. Zones in the same region are in nearby areas.
  • C. Communication between zones has latency and may be charged. The purpose is not speed or cost but preparing for failures.
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