Document GCS bucket retention policy impact on ClickHouse storage #147
Description
Problem
The current GCS documentation (content/en/altinity-kb-integrations/altinity-kb-google-s3-gcs.md) only covers basic setup (HMAC keys, endpoint configuration) but doesn't mention an important operational caveat.
Missing Information
When a GCS bucket has a retention policy enabled, objects cannot be deleted until the retention period expires. This causes issues with ClickHouse because it regularly deletes data during:
- Part merges - old parts are removed after merge
- Mutations - replaced data is deleted
- TTL expiration - expired data is purged
If the bucket retention policy prevents deletion, old data accumulates and storage grows exponentially, leading to unexpected costs and potential operational issues.
Suggested Addition
Add a warning/note to the GCS documentation explaining:
- Bucket retention policies prevent ClickHouse from deleting obsolete data
- This causes continuous storage growth
- Recommendation to disable retention policy or use a bucket without one for ClickHouse storage
If this seems like a good enhancement, I'd be happy to take this up and submit a PR.