I just installed signoz on our production cluster a week ago getting this error on clickhouse DB, Does this mean the volume is full? Also attaching the file system of node machine. Btw. the persistant volume is of default capacity ie 20GB

yes, it is. You will need to increase ClickHouse storage.

Is there a way to debug the issue, like downloading the existing database or at-least being able to connect to the database externally ?

Is it not possible for you to increase the CH PV size more than default 20Gi?

It is definitely possible just want to optimize the existing system prior to doing that because it has just been a week, so quite surprising that 20GB is full already.