PCA Storage & Retention Flashcards
6 cards from real PCA practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 PCA Storage & Retention flashcards as text
What file format do Prometheus TSDB chunk files use?
Answer: A custom binary format optimized for time-series compression
Prometheus TSDB uses a custom binary chunk format with delta-of-delta and XOR compression for timestamps and values.
What happens to the WAL when Prometheus shuts down cleanly?
Answer: It is checkpointed so replay on restart is faster
On a clean shutdown, Prometheus creates a WAL checkpoint that truncates fully-compacted segments, speeding up the next startup.
Which Prometheus command-line flag specifies the directory where TSDB data is stored?
Answer: --storage.tsdb.path
The --storage.tsdb.path flag sets the directory where Prometheus writes all its TSDB blocks and WAL.
What is the purpose of the `meta.json` file inside a Prometheus TSDB block directory?
Answer: It stores the block's time range, version, statistics, and compaction history
meta.json is the block's manifest, recording its min/max time, ULID, number of series, and compaction ancestry.
Why might setting a very short TSDB retention period cause high disk I/O in Prometheus?
Answer: Frequent block deletions and compactions run more often to purge data quickly
Short retention causes Prometheus to compact and delete blocks more frequently, increasing background disk activity.
Which tool is commonly used alongside Prometheus to provide long-term, highly-available storage without modifying Prometheus itself?
Answer: Thanos
Thanos extends Prometheus with global querying, long-term object storage (e.g., S3), and multi-cluster HA using sidecars.