Respect to the Kafka team as Kafka is an incredible piece of software, but the Mongo guys got torched for eternity for pulling the same shenanigans.
https://jack-vanlightly.com/blog/2023/4/24/why-apache-kafka-...
Kafka has never tried to hide that fact and it does not, in any way, make Kafka unsafe.
Benchmarking a system that fsyncs every write to one that doesn't isn't an apples-to-apples comparison. You are free to make the argument that you might not need them, but if you are benchmarking systems and one of them fsyncs by default, that is the level of durability I'm going to expect, otherwise I can assume the other guy will be just as fast if he turns off fsyncs as well.
With the usual recommended settings, XFS filesystem, 3 replicas, 2 "in-sync" replicas, etc., it is rather safe. You can also tune background flush to your liking.
The above tradeoffs are very reasonable and Kafka runs very fast on slow disk s(magnetic or in cloud), and even faster on SSD/NVMe disks.
PS: I really miss working with mongodb. It's been almost 7 years since I last used it. I'm surprised I don't see it mentioned very often anymore.
MongoDB has always seemed to place write consistency secondary to other priorities (mostly sales / read / features) which is frankly a crap way to do a database, much less a distributed one. And I am so sick of MongoDB basically saying "no it's fixed in the new version" which is always a major red flag.
Right now it's getting its lunch eaten by Postgres's document interface from what I can tell.
b) MongoDB has been growing revenue ~40% year on year for the last few years.
c) PostgreSQL is only a serious competitor for MongoDB if you have small datasets. After all these years PostgresSQL still is ridiculously poor when it comes to clustering, replication etc. Everyone's solution of "just buy a bigger instance" is just laughable.
Which is why his papers are so great.
But the MongoDB one was "wow this is bad".
I assume you have an example of one that wasn't ?
Cassandra doesn't do that, consistency level is fundamental to the documentation and user guide. That is AWFUL.
"Curiously, MongoDB omitted any mention of these findings in their MongoDB and Jepsen page. Instead, that page discusses only passing results, makes no mention of read or write concern, buries the actual report in a footnote, and goes on to claim:
MongoDB offers among the strongest data consistency, correctness, and safety guarantees of any database available today.That is fraud. That is clownshow. Enjoy your increasing revenue.
And single node is a perfectly fine default for most use cases.
After all Cassandra's default consistency level is 1.
Hence my point there is no difference in defaults between MongoDB and Cassandra.
Certainly, not all Jepsen reports are all that bad, and tbh I'm at leaast as interested in the way the vendors respond (some of which have been terrible).
And those that actually had tried it were aware that every client enabled fsync out of the box. So in fact the entire situation was seriously overblown.
But sure let irrational ideology affect your technology decisions. That will work out well.
Not everyone has time to review every single line of code in their tech stacks. Past reputation is important, and your replies here don't seem to be of much help to MongoDB's reputation as far as I can tell.