PCA PCA Storage & Retention

Question 1

What is the default local storage retention period for Prometheus time-series data?

Accepted Answer

15 days

Answer

By default, Prometheus retains local data for 15 days before it is deleted.

Question 2

Which Prometheus storage format organizes data into time-based directories called blocks?

Accepted Answer

TSDB (Time Series Database)

Answer

Prometheus uses its own TSDB which stores data in immutable time-based blocks on disk.

Question 3

Which flag sets the maximum amount of disk space Prometheus can use for local storage?

Accepted Answer

--storage.tsdb.retention.size

Answer

The --storage.tsdb.retention.size flag caps how much disk Prometheus uses, deleting old blocks when the limit is reached.

Question 4

What is the Write-Ahead Log (WAL) in Prometheus TSDB used for?

Accepted Answer

Durably recording incoming samples before they are compacted into blocks

Answer

The WAL ensures that data received by Prometheus is not lost if the process crashes before samples are flushed to a block.

Question 5

How long does Prometheus keep data in memory before writing it to a disk block by default?

Accepted Answer

2 hours

Answer

Prometheus accumulates data in a head block in memory for approximately 2 hours before compacting it to disk.

(PCA) Prometheus Certified Associate Practice Test