6 ms·
None of this is guaranteed by default. By default, writes are flushed every 60 seconds. By default, there's no journaling. How can one claim full consistency if
by batasrki 15y ago
None of this is guaranteed by default. By default, writes are flushed every 60 seconds. By default, there's no journaling. How can one claim full consistency if the the former two points are true?
Don't get me wrong, I love mongo. I'm building a web app backed by it. But the marketing talk is grating, which whT this post nails.
- mathias_10gen 15y agoI think those two issues are orthogonal to consistency. In ACID, consistency and durability are two different letters and CAP doesn't even mention durability. Are you referring to another definition of consistency?
- batasrki 15y agoHow is flushing a write every 60 seconds orthogonal to consistency? If there's a server crash between the write to RAM and the subsequent flush, the data is lost, is it not? How do you guarantee the data is there in that case?
- stonemetal 15y agoThat would mean the data set was not durable, it doesn't speak to consistency at all. DB consistency is about transaction ordering. Transaction 1 always comes before transaction 2, but 2 may exist or not as it pleases. Transaction 1 must be present if 2 is present.