diff --git a/docs/introduction/comparison.md b/docs/introduction/comparison.md index b65813207..88d48849e 100644 --- a/docs/introduction/comparison.md +++ b/docs/introduction/comparison.md @@ -56,10 +56,12 @@ RRD-style database that expects samples to arrive at regular intervals. Every time series is stored in a separate file, and new samples overwrite old ones after a certain amount of time. -Prometheus also creates one local file per time series, but allows storing -samples at arbitrary intervals as scrapes or rule evaluations occur. Since new -samples are simply appended, old data may be kept arbitrarily long. Prometheus -also works well for many short-lived, frequently changing sets of time series. +[Prometheus's local TSDB](/docs/prometheus/latest/storage/#on-disk-layout) keeps +recent samples in an in-memory head protected by a write-ahead log, then +persists them in time-based block directories containing a chunks directory, an +index, and metadata. It accepts samples at arbitrary intervals as scrapes or +rule evaluations occur. Retention is configurable, and Prometheus also works +well for many short-lived, frequently changing sets of time series. ### Summary @@ -107,8 +109,8 @@ Prometheus, by contrast, supports the float64 data type with limited support for strings, and millisecond resolution timestamps. InfluxDB uses a variant of a [log-structured merge tree for storage with a write ahead log](https://docs.influxdata.com/influxdb/v1.7/concepts/storage_engine/), -sharded by time. This is much more suitable to event logging than Prometheus's -append-only file per time series approach. +sharded by time. This is more suitable for event logging, while Prometheus's +block-based local TSDB is optimized for monitoring time series. [Logs and Metrics and Graphs, Oh My!](https://grafana.com/blog/2016/01/05/logs-and-metrics-and-graphs-oh-my/) describes the differences between event logging and metrics recording.