Quick tech explanation for the border:
There are two ways the world save file can exist, on the hard drive where space isn't an issue, or in a "ram disk" which is in the temporary memory.
On the hard disk space isn't an issue, like I mentioned. However, hard disks are slow compared to a computers RAM. Everytime you place/destroy a block the game saves the change on the disk. A lot of changes at once means a lot of writing to the hard disk. On a shared server like ours it can be slow. This is the lag many experience when placing/destroying blocks.
The other option is a RAM disk. Linux servers (like ours) give us the option of detaching a portion of RAM and treating it like a poser hard disk. The minecraft server doesn't know the difference, but being in RAM the saving block place/destroy is a lot faster. However, it does take away the memory available to the server itself. The bigger the world save file, the more RAM needed for this poser disk. Some fool could go out and explore a TON of the world, making the world save larger. This causes RAM use for the save file to increase.
The function of the boarder is to keep the world save from getting too big and eating up the space in RAM. So the trade off is a lot of space on the slow hard drive, or using the fast RAM but making sure not too much is taken up by the save file so the server has more room for the rest of the program.
DrMo/DAKLER, can you tell me the specific error you are getting?