04-26-2015, 02:39 AM
Let me give you a quick explanation of minecraft performance:
All minecraft servers, regardles of their underlying technology, will need to accomodate chunks around each player in RAM. Let's find the upper bound of such RAM usage. Say you want to guarantee the minimum viewdistance of 4 chunks in each direction. This means each player will have up to (4 + 1 + 4) * (4 + 1 + 4) = 81 chunks loaded for them. In the worst case scenario, each player is in a different location and none of their loaded chunks overlap. For a thousand players, this means 81.000 chunks loaded in the RAM and processing events. If you consider an average chunk being 1/3 used (has non-air blocks in 6 sections out of the 16 vertical sections), this means that the server needs to hold 81.000 * 6 = 486.000 chunk sections in the memory. Each section contains block types, block metadata, skylight and blocklight values, which comes to 10.240 raw bytes. Your current RAM demands are thus 486.000 * 10.240 = 4.976.640.000 bytes, or some 4750 MiB of RAM. And that's just the absolute minimum of data, your players won't be happy with a viewdistance of 4; doubling the viewdistance effectively quadruples the amount of data needed, so for a viewdistance of 8 you'd need more than 19 GiB of RAM for 1000 players. Next, my semi-qualified estimate is that the additional housekeeping data will take about 20% of the base RAM, so we're at 23 GiB of RAM. Still convinced this is viable?
I'm pretty sure you'll reach the CPU bounds earlier than the RAM bounds. However, there's not an easy way to provide any kind of estimate. Let's try this: The server will have to "tick" mobs in all the loaded chunks. That means that each chunk will get scanned, mobs will drown / suffocate / burn / fall / pathfind. This means that all that chunk data we've calculated earlier will need to be read, at least 20 times per second, to provide a reasonable gameplay. This meand 23 GiB * 20 ticks / second = 460 GiB / second.
If we are to trust the RAM benchmarks here: http://www.memorybenchmark.net/read_unca...intel.html , we should assume that current technology can read up to 20 GiB per second - nowhere near the value we need!
All minecraft servers, regardles of their underlying technology, will need to accomodate chunks around each player in RAM. Let's find the upper bound of such RAM usage. Say you want to guarantee the minimum viewdistance of 4 chunks in each direction. This means each player will have up to (4 + 1 + 4) * (4 + 1 + 4) = 81 chunks loaded for them. In the worst case scenario, each player is in a different location and none of their loaded chunks overlap. For a thousand players, this means 81.000 chunks loaded in the RAM and processing events. If you consider an average chunk being 1/3 used (has non-air blocks in 6 sections out of the 16 vertical sections), this means that the server needs to hold 81.000 * 6 = 486.000 chunk sections in the memory. Each section contains block types, block metadata, skylight and blocklight values, which comes to 10.240 raw bytes. Your current RAM demands are thus 486.000 * 10.240 = 4.976.640.000 bytes, or some 4750 MiB of RAM. And that's just the absolute minimum of data, your players won't be happy with a viewdistance of 4; doubling the viewdistance effectively quadruples the amount of data needed, so for a viewdistance of 8 you'd need more than 19 GiB of RAM for 1000 players. Next, my semi-qualified estimate is that the additional housekeeping data will take about 20% of the base RAM, so we're at 23 GiB of RAM. Still convinced this is viable?
I'm pretty sure you'll reach the CPU bounds earlier than the RAM bounds. However, there's not an easy way to provide any kind of estimate. Let's try this: The server will have to "tick" mobs in all the loaded chunks. That means that each chunk will get scanned, mobs will drown / suffocate / burn / fall / pathfind. This means that all that chunk data we've calculated earlier will need to be read, at least 20 times per second, to provide a reasonable gameplay. This meand 23 GiB * 20 ticks / second = 460 GiB / second.
If we are to trust the RAM benchmarks here: http://www.memorybenchmark.net/read_unca...intel.html , we should assume that current technology can read up to 20 GiB per second - nowhere near the value we need!