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Exactly I will never ever try MongoDB because of that. A database that do not fsync should not be called a database.

by skyde 3y ago

deleted 3y ago
[deleted]
nezirus 3y ago
Kafka doesn't do any stupid tricks, but uses the underlying platform for the full potential: https://kafka.apache.org/documentation/#linuxflush https://kafka.apache.org/documentation/#linuxflush 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.
uberduper 3y ago
MongoDB moved on from mmap at version ~3.6. WiredTiger can be configured to fsync every commit. Enjoy trying MongoDB! 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.
- AtlasBarfed 3y ago
  Last I heard of MongoDB it was getting utterly buried by the Jepsen guy, and for anyone that follows distributed systems at some technical level, that is damning. He finds stuff wrong with everything, but that one was particularly damning. 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.
  - threeseed 3y ago
    a) Every distributed database has had serious issues with Jepsen. 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.
    - KptMarchewa 3y ago
      Growing revenue of a owner company as a argument for database? We have an Oracle fan here.
    - AtlasBarfed 3y ago
      Jepsen does find stuff with everything. Thus you have to know what is being discussed is serious and blatantly bad, or just the usual "wow distributed is hard". Which is why his papers are so great. But the MongoDB one was "wow this is bad".
      - threeseed 3y ago
        Every distributed database has been "wow this is bad". I assume you have an example of one that wasn't ?
        AtlasBarfed 3y ago
        "MongoDB’s default level of write concern was (and remains) acknowledgement by a single node, which means MongoDB may lose data by default." 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.
datadeft 3y ago
Kafka is not a database....
- postalrat 3y ago
  Maybe you could say that if it acted like redis pub/sub and nothing was stored.
threeseed 3y ago
MongoDB has been doing fsync by default for over a decade now . 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.
- hnfong 3y ago
  Avoiding a database that has a proven historical record of disregarding data consistency and resorting to marketing gimmicks is "irrational ideology"? 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.

Exactly I will never ever try MongoDB because of that. A database that do not fsync should not be called a database.

by skyde 3y ago

Exactly I will never ever try MongoDB because of that. A database that do not fsync should not be called a database.

deleted 3y ago

[deleted]

nezirus 3y ago

Kafka doesn't do any stupid tricks, but uses the underlying platform for the full potential: https://kafka.apache.org/documentation/#linuxflush https://kafka.apache.org/documentation/#linuxflush 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.

uberduper 3y ago

MongoDB moved on from mmap at version ~3.6. WiredTiger can be configured to fsync every commit. Enjoy trying MongoDB! 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.

AtlasBarfed 3y ago
Last I heard of MongoDB it was getting utterly buried by the Jepsen guy, and for anyone that follows distributed systems at some technical level, that is damning. He finds stuff wrong with everything, but that one was particularly damning. 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.
- threeseed 3y ago
  a) Every distributed database has had serious issues with Jepsen. 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.
  - KptMarchewa 3y ago
    Growing revenue of a owner company as a argument for database? We have an Oracle fan here.
  - AtlasBarfed 3y ago
    Jepsen does find stuff with everything. Thus you have to know what is being discussed is serious and blatantly bad, or just the usual "wow distributed is hard". Which is why his papers are so great. But the MongoDB one was "wow this is bad".
    - threeseed 3y ago
      Every distributed database has been "wow this is bad". I assume you have an example of one that wasn't ?
      - AtlasBarfed 3y ago
        "MongoDB’s default level of write concern was (and remains) acknowledgement by a single node, which means MongoDB may lose data by default." 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.

datadeft 3y ago

Kafka is not a database....

postalrat 3y ago
Maybe you could say that if it acted like redis pub/sub and nothing was stored.

threeseed 3y ago

MongoDB has been doing fsync by default for over a decade now . 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.

hnfong 3y ago
Avoiding a database that has a proven historical record of disregarding data consistency and resorting to marketing gimmicks is "irrational ideology"? 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.