Add note to the changelog about write iops

services/horizon/CHANGELOG.md

@@ -14,6 +14,7 @@ file. This project adheres to [Semantic Versioning](http://semver.org/).
 ### Features
 
 * New feature, enable captive core based ingestion to use remote db persistence rather than in-memory for ledger states. Essentially moves what would have been stored in RAM to the external db instead. Recent profiling on the two approaches shows an approximate space usage of about 8GB for ledger states as of 02/2022 timeframe, but it will gradually continue to increase as more accounts/assets are added to network. Current horizon ingest behavior when configured for captive core usage will by default take this space from RAM, unless a new command line flag is specified `--captive-core-use-db=true`, which enables this space to be taken from the external db instead, and not RAM. The external db used is determined be setting `DATABASE` parameter in the captive core cfg/.toml file. If no value is set, then by default it uses sqlite and the db file is stored in `--captive-core-storage-path` - ([4092](https://github.com/stellar/go/pull/4092))
+  * Note, if using this feature, we recommend using a storage device with capacity for at least 3000 write ops/second.
 
 ### Fixes