I was having the exact same problem in 1.17.1. I was very confused why my server was lagging so much when players were exploring new chunks. When I found out it was due to this setting I was very surprised. Like the opener of this issue stated this is terrible for world files stored on HDD's because HDD's aren't well-suited for random IO. Using the DSYNC option for file I/O doesn't give the OS a chance to coalesce these writes resulting in 100% disk activity at a puny write speed of around 700KB/s. While the disk is busy writing at those slow speeds the server is waiting for the write call to complete. With sync-chunk-writes set to false the disk is active for very short periods of time writing at several megabytes per second. As expected moving the world files over to an SSD alleviates the issue somewhat.
https://www.minecraft.net/en-us/article/minecraft-snapshot-20w14a The original motivation for this change was that it should prevent data loss or corruptions in the case of a crash. I don't think this is a good argument. As soon as the write system call has completed it's the operating system's job to commit the changes to disk at it's discretion. By default the linux kernel flushes queued data every 5 seconds, or when free memory goes below a certain limit. The only reason that the operating system wouldn't get the chance to commit to disk is when the entire system goes down unexpectedly (like power outages) in which case all bets are off in terms of data integrity anyway.
goeiecool9999
I was having the exact same problem in 1.17.1. I was very confused why my server was lagging so much when players were exploring new chunks. When I found out it was due to this setting I was very surprised.
Like the opener of this issue stated this is terrible for world files stored on HDD's because HDD's aren't well-suited for random IO. Using the DSYNC option for file I/O doesn't give the OS a chance to coalesce these writes resulting in 100% disk activity at a puny write speed of around 700KB/s. While the disk is busy writing at those slow speeds the server is waiting for the write call to complete. With sync-chunk-writes set to false the disk is active for very short periods of time writing at several megabytes per second.
As expected moving the world files over to an SSD alleviates the issue somewhat.
https://www.minecraft.net/en-us/article/minecraft-snapshot-20w14a
The original motivation for this change was that it should prevent data loss or corruptions in the case of a crash. I don't think this is a good argument. As soon as the write system call has completed it's the operating system's job to commit the changes to disk at it's discretion. By default the linux kernel flushes queued data every 5 seconds, or when free memory goes below a certain limit. The only reason that the operating system wouldn't get the chance to commit to disk is when the entire system goes down unexpectedly (like power outages) in which case all bets are off in terms of data integrity anyway.
https://old.reddit.com/r/admincraft/comments/hn0g84/syncchunkwrites_causing_lag/
There are more people who complained about this and it seems that unofficial servers like paper ignore the sync-chunk-writes property and hide it as a command line flag instead.
For those reasons I think this issue should be reopened.