[skyde]

Author say "Redpanda incorrectly claim Kafka is unsafe because it doesn’t fsync - it is not true".

If you don't Fsync the batch, it's possible the server would send response to client saying data was written successfully while the batch is still just in memory and then the server loose power and never write it to disk.

Maybe the author have a different definition of unsafe but to me if it's not ACID it's unsafe!

[EdwardDiego]

Kafka won't ack to the producer in default conf until the replicas have acked to the leader.

[skyde]

A topic partition can lose some messages without compromising the correctness of the data replication protocol itself.

But I don't think anyone would call a configuration where you ca lose message a safe configuration.