> Why would I use ClickHouse instead of storing log data as json file for historical log data?

There are multiple reasons:

1. Databases optimized for logs (such as ClickHouse or VictoriaLogs) store logs in a compressed form, where values per every log field are grouped and compressed individually (aka column-oriented storage). This results in smaller storage space comparing to plain files with JSON logs, even if they are compressed.

2. Databases optimized for logs perform typical queries at much faster speed comparing to grep over JSON files. Performance gains may be 1000x and more because these databases skip reading unneeded data. See https://chronicles.mad-scientist.club/tales/grepping-logs-re...

3. How are you going to grep 100 petabytes of JSON files? Databases optimized for logs allow querying such amounts of logs because they can scale horizontally by adding more storage nodes and storage space.