Bernhard Gräuler
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Attached some iotop screenshots. First one created shortly after I started the server, and for the last one, created around 60 minutes after startup, I messed up switching from thread to process view, expecting iotop to summarize the values. Yet, it actually resets the counters, so the values in the last screenshot must be added to the previous one, and the count between 30m and my mess-up is lost.
I also tailed the server log printing the connected players from time to time. This is a server I use to play the game with my kids, so as they are in school right now...
I investigated this a little further. Using fatrace i was able to find the file the server constantly accesses for write, it's a world region file (/usr/local/games/minecraft/world/region/r.0.0.mca)
In addition to that I created a VisualVM Application snapshot with some thread dumps and profiler snapshots, and attached it here. Hopefully this helps identifying the issue...
Ok, this is weird. I moved away from the spawn point and the problem went away. Then, I deleted the world and created a new one. The issue is not reproducible anymore. Wondering what system component (HW/SW) might cause that effect.
The issue also occurs in version 1.10.2. I just upgraded the game, created a new world in single player mode. It happens with every block I destroy (tried dirt, leaves, wood and a mushroom). After several seconds the block disappears and drops the item.
For older versions this but was reported to be related to network lagging.
Win 7, 64bit, Java 8, latest.
I also can confirm this must be related to redstone-repeater clocks and / or hoppers. Can't say for sure, what exactly causes it, yet, but as soon as I deactivated those circuits the writing stopped.