How to remove lag that lasts 2 minutes on my server?

My server is working properly and I allocated enough RAM on it (4GB) but as soon as my friends join they like for about 2 minutes then unlag afterwards, and if they die they lag for 2 minutes again!
Please help!

Added (1). Oh sorry, the game is Minecraft

What's wrong with my minecraft? - 2

So, the other day my servers stopped connecting or working, so i deleted my.minecraft file and delted minecraft, then i reinstalled it, after i did the minecraft won't load, the blue downloading bar comes up to install the files, but then the blue bar vanishes and nothing happening, i press play again then it does the same thing, it just says its installing files and then vanishes. I have played minecraft for months and its been fine, what is happening, how do i fix this? I have updated my Java and done everything with that? I'm running windows 7

We need Players and Builders for our Minecraft server?

We're a developing minecraft server with many plugins kind staff and a nice map.
We have everything from minigames to factions and economy. We would love to have some more players who are responsible. Come and maybe you will become staff. TY

Minecraft skyblock server?

Does anyone know a good skyblock server? I used to play on one with my brother a few versions ago and then we stopped now we wanted to play again have our same island and such. They had economy and in the shop there were pictures of the items you would buy. They had built a PVP dome that was a small area with trees and such. They had how to make a cobblestone generator and big pixel art in the lobby(floating). Other people were allowed to visit your island if you let them. They even had a trading post.

What is a good Pixelmon server?

Looking for a good, newer Pixelmon Minecraft server to play on with my friends.
(For all experience levels)

Why does minecraft crash when i try to join a server?

My minecraft crashes when ever i try to join a server i mean i will join it will all load i will see spawn and BOOM minecraft crashes after a few seconds of seeing the spawn and players this happens on all the servers i try to go on yet single player seems fine =

How to change the thumnail on Enjin?

I have a profile for a minecraft server on Enjin. I'm trying to change the little thumbnail that shows up on my wall but I can't figure out how. Everyone else has their minecraft character's face as their thumbnail but I see nowhere to get it changed.

Profile: http://www.endgameserver.com/profile/9822878

Error: Unable to access jarfile Minecraft?

I have created a custom modpack along with a server also. When I launch the "Minecraft Server.jar" file everything works fine, and I'm also able to connect on my client. However, I need to increase the amount of allocated ram.

I created a run.bat file, with the following text. Java -Xms1G -Xmx2G -jar Minecraft Server.jar -o true pause

I then get the error "Error: Unable to access jarfile Minecraft" after launching the cmd.

I'm the latest version of 64bit java on a 64 bit system, so that is not the problem.