EX294 Coordinate rolling updates Practice Question
A junior administrator needs to perform a rolling update of 8 web servers where exactly 2 servers are updated at a time. Which play-level keyword and value should be used in the Ansible playbook?
⚠ Common exam trap
The trap here is mixing up forks, which controls parallel connections, with serial, which controls rolling batch size.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
serial: 2
The serial keyword is the standard way to define rolling update batch size in an Ansible play. Setting serial: 2 causes the play to process two hosts at a time through the full task list, ensuring only two of the eight web servers are updated concurrently. This is the direct and correct control for the administrator's requirement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
throttle: 2
Why it's wrong here
throttle limits how many hosts execute a single task concurrently, but it does not define rolling batches. Without serial, Ansible still targets all 8 hosts in the play, so throttle: 2 would not produce the required two-at-a-time update behavior across the whole task list.
- ✗
max_fail_percentage: 2
Why it's wrong here
max_fail_percentage defines a failure threshold, not a batch size. Setting it to 2 means the play aborts if more than 2 percent of hosts in a batch fail, which does not control how many servers are updated simultaneously and is unrelated to the stated requirement.
- ✗
forks: 2
Why it's wrong here
forks controls how many hosts Ansible contacts in parallel across the entire inventory, not the rolling batch size. Setting forks: 2 would still attempt to run the play on all 8 hosts, just with two parallel connections, which does not meet the requirement of updating exactly two servers at a time.
- ✓
serial: 2
Why this is correct
serial: 2 instructs Ansible to process hosts in batches of two during the play. Each batch completes the full task list before the next batch begins, so exactly two servers are updated at a time, which matches the administrator's requirement for this 8-node fleet.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Red Hat exam blueprint
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