This release uses Write-Ahead Logging (WAL) for the remote_write API. This currently causes a slight increase in memory usage, which will be addressed in future releases.
* [CHANGE] Default time retention is used only when no size based retention is specified. These are flags where time retention is specified by the flag `--storage.tsdb.retention` and size retention by `--storage.tsdb.retention.size`. #5216
* [CHANGE] `prometheus_tsdb_storage_blocks_bytes_total` is now `prometheus_tsdb_storage_blocks_bytes`. prometheus/tsdb#506
* [FEATURE] [EXPERIMENTAL] Time overlapping blocks are now allowed; vertical compaction and vertical query merge. It is an optional feature which is controlled by the `--storage.tsdb.allow-overlapping-blocks` flag, disabled by default. prometheus/tsdb#370
* [ENHANCEMENT] Use the WAL for remote_write API. #4588
