PCA PCA Storage & Retention 1 — Questions and Answers
Question 1: What is the default local storage retention period for Prometheus time-series data?
- 15 days (Correct answer)
- 30 days
- 7 days
- 90 days
Correct answer: 15 days
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?
- TSDB (Time Series Database) (Correct answer)
- LevelDB
- RocksDB
- InfluxDB line protocol
Correct answer: TSDB (Time Series Database)
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?
- --storage.tsdb.retention.size (Correct answer)
- --storage.tsdb.max-disk
- --storage.local.max-size
- --tsdb.disk-limit
Correct answer: --storage.tsdb.retention.size
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?
- Durably recording incoming samples before they are compacted into blocks (Correct answer)
- Pre-computing recording rules before they run
- Streaming metrics to remote storage in real time
- Logging HTTP scrape requests for debugging
Correct answer: Durably recording incoming samples before they are compacted into blocks
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?
- 2 hours (Correct answer)
- 15 minutes
- 24 hours
- 1 hour
Correct answer: 2 hours
Prometheus accumulates data in a head block in memory for approximately 2 hours before compacting it to disk.
Question 6: What does Prometheus do when its local disk retention limit is reached?
- Deletes the oldest TSDB blocks first (Correct answer)
- Stops accepting new scrapes
- Writes excess data to remote_write only
- Compresses all blocks to save space
Correct answer: Deletes the oldest TSDB blocks first
When the retention limit is hit, Prometheus removes the oldest data blocks to free disk space.
PCA PCA Storage & Retention 1
What is the default local storage retention period for Prometheus time-series data?