There are some questions on this already, but many of them seem to apply to 1.9 only, or be caused by a broken version of Java. What I want to know instead is how to actually determine the bottleneck myself.

How can I tell if it's RAM? (And if it is, can a swapfile fix this?)
Do I have the Java -Xmx etc. parameters set incorrectly?
Is it the CPU, the network connection itself, something else?

I'm asking for a troubleshooting guide, not a solution for one specific situation or modpack (which, in my case, would be a Hexxit server on a Raspberry Pi 3 with OSMC)

  • Wouldn't this be dependent on the computer running the world? Bottlenecks are generally the slowest component, which depends on a variety of factors, such as current load, number of mods, playerbase, etc. – Frank Jan 27 '18 at 19:00
  • @Frank The question is a) whether there is a specific component specifically responsible for blocks reappearing and b) how the responsible component can be identified. "slowest" is not that precise a description when you compare e.g. RAM to HDD – Zommuter Jan 27 '18 at 19:03
  • Yeah, but what you're asking is far too broad; you're asking us how to basically do basic PC troubleshooting. There's not really much here that's specific to Minecraft, or any specific game, for that matter. – Frank Jan 27 '18 at 19:09
  • @Frank I beg to differ - looking e.g. for specific messages in the server log (such as the "can't keep up" which might indicate the CPU) is far more specific than general troubleshooting (which might actually make for a good blog entry I guess) – Zommuter Jan 27 '18 at 19:18
  • 1
    There are a lot of very broad questions on this site, for example the list of error messages in Minecraft, yet they are very helpful (mainly to get rid of crash questions 😁). This would also be good. Basically it asks what to do against/how to detect the cause of server lag. For client lag, there's Shift+F3, but for servers it's harder to find the source. – Fabian Röling Jan 27 '18 at 19:33

A basic troubleshooting guide(by no means conclusive, and based on personal experience): For determining the actual cause, try changing settings, disabling/enabling mods, and seeing if anything changes. If it changes for the better, you're going in the right direction. Minecraft has so many different aspects, it's very hard to figure out the exact problem.

Step 1: Know your mods. Certain mods will interact badly with each other, e.g. Logistics pipes and EE2, when hooked up together, make a lot of lag. Step 2: As you mentioned, RAM is important. Everything depends on how many mods you are running, how many players you have, how many dimensions and chunks etc. If you haven't dedicated enough RAM, or have used the wrong arguments, you'll be slow on everything. For reference, the right way to dedicate the RAM is: -Xmx[amount of memory maximum, followed by the measurement of it, e.g. 4G, 512M] -Xms[amount of memory minimum, same format]

Step 3: As previously mentioned, certain devices can cause lag. Get notifications on your server saying that 'lag causing devices will be removed, and the player who owns them may be punished', or something to a similar effect. If this doesn't work, consider a world reset.

Step 4: If none of the above options are effective, consider investing in better hardware, or a server hosting provider with a good reputation and non-ripoff prices. CreeperHost is apparently very good, but I've never personally used them. Good luck!

Side note: a Hexxit server on a Pi? You can run a vanilla MC server on a Pi without too much difficulty, but Hexxit... Not optimistic.

  • I managed to get Hexxit running on my Pi3, and it worked fine for my. However my friend experienced the block lag via Internet, despite the connection being fine, so I'm rather confused... – Zommuter Feb 22 '18 at 11:07
  • Thanks for your input, is there any way to profile mod performance or is this really a trial and error of switching individual mods on and off. Or is at least some divide&conquer possible? – Zommuter Feb 22 '18 at 11:09
  • Impressed you got Hexxit running. Some mods will definitely lag more than others, but block lag tends to be a sign of machines or lag-heavy areas lagging the rest of the server. Sorry I can't be more specific, but there are thousands of mods, all of which can lag stuff. – tomskeet18 Feb 23 '18 at 12:11

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