Problem Errors on start-up and lagging

[Infallible83]

Hi all,

I am an inexperienced helper on a dedicated server and a few of us are scratching our heads over why we are getting such bad lag. Please excuse any stupid questions as I am very new to this.

MOD PACK - Monster

SETUP - We have an OVH dedicated server with excellent performance. Intel Xeon E5-1650v2 with 64GB RAMhttp://www.ovh.co.uk/dedicated_servers/infra/2014-EG-64.xml

PROBLEMS

1) Currently when the server starts, it will list a few SEVERE errors such as the following:

2014-02-18 15:47:14 [SEVERE] [ForgeModLoader] The mcmod.info file in Reliquary-1.6.4-1.1.1.jar cannot be parsed as valid JSON. It will be ignored

Probably a stupid question but does this mean we have set something up wrong or is this something that happens with the larger mod packs?

2) We are only a small community of circa 5 regular players but never more than 8, yet at times we suffer from horrendous lag, so much so that it is virtually unplayable. Are there any serious watchouts that I should be aware of that might cause intermittant lag. (I have read JadedCats helpful threads on known issues a good practice for server administration). Also, I am 99% sure that we dont have anything obvious in game such as power loops, we dont have any mistcraft ages, we only have 2 chunk loaders up currently and we have one mining world and as of now, no one has even been to the deep dark.

If it is helpful here is a copy of the full server log - http://legendgp.com/download/ForgeModLoader-server-2.log
And this is a list of the arguments we are using currently - will paste link shortly.

Any help is greatly appreciated.

Thanks

Infallible

 

[lenscas]

2014-02-19 13:40:50 [FINE] [ForgeModLoader] The world 41bcead5 (world) may have leaked: seen 7845 times.
Because of this I suspect a memory leak. If it is then you just need to reboot the server once in a while.

 

[Infallible83]

Thank you very much, I know we are not the best at restarting the server. I will look at getting an automated 3/4 hour restart schedule.

However, there are times that it will lag immediately after restart, is there anything else that might be causign that?

Thanks in advance,

Infallible83

 

[Francis Baster]

I wouldn't be too concerned about warnings or even severes in your server log, unless you can tell from the message that there is a serious problem. It is common for some mods to give severe messages for the most harmless of errors. The JSON error you are getting just meant that some mod author didn't provide the correct mod description file, which is hardly the end of the world.

My advice would be to connect to your server remotely using Java VisualVM and monitor what is going on with your CPU, heap space, and perm gen space. This will quickly show if the lag is caused by a CPU or memory bottleneck. You can also sample the CPU using JVisualVM to see what methods it is spending time inside, which may help reveal the source of the lag if CPU bottleneck is responsible. I would also advise installing mods like aPerf and Opis. These will let you see if you have an entity overflow, which can cause crippling lag, or even tile entities which have glitched out and are sucking up way more CPU cycles than they should.

I should also ask how much memory you have allocated to Minecraft. I noticed your dedicated server has 64GB available, but I would advise against giving this all to Minecraft or this could cause inefficiencies (lag). With Minecraft you either have enough memory or you don't. There is no benefit to having more than you need. I think sk89q said something about that here:
http://www.sk89q.com/2013/03/improving-your-minecraft-servers-performance/

If you are wondering how to use JVisualVM to connect to a process which is not running on your computer, the process is as follows:
1) Add these arguments to your server start script:

-Dcom.sun.management.jmxremote.port=1098
-Dcom.sun.management.jmxremote.ssl=false
-Dcom.sun.management.jmxremote.authenticate=false

2) Open JVisualVM and click File -> add remote host. Specify the IP address / URL of your server.
3) Right click your remote host in the left hand panel, and click add JMX connection.
4) Enter your server's IP address / URL followed by the port number you specified in the start script, for example 192.168.1.1:1098.
5) Right click the JMX connection and click open.
6) Head over to the monitor tab and wait a few seconds for the graphs to render.

If your CPU graph shows the garbage collection is running all the time, this means that your server is out of memory. The memory bar climbing to the max -Xmx value and then dropping back down is normal Java behaviour, and does not indicate that you are out of memory.

On the CPU graph scale, 100% means all cores are at full capacity. As your CPU has 6 cores, and the Minecraft server is mostly single-threaded, a CPU usage of 16.7% or greater means that your Minecraft server is using all the CPU cycles that your hardware can give it. The exception is if you have CPU intensive plugins which run on a separate thread such as dynmap, in which case a usage above 16.7% could be OK.

 

[Infallible83]

Thank you very much for your reply.

I will try this tonight.

With reference to the RAM, we originally had 32GB assigned but then reduced it to 8GB after reading about lag caused by memory dumping. I will try out various GB to see what garbage collection tells me is correct.

Again thank you very much for your responce.

Infallible