Hi. I have a question regarding chunks and how the server handles them. From my understanding, the server keeps 5 chunks loaded around the player and no more than that.

Does the 5 "chunks to load" affect vertical distance? For instance, if I build a mob farm at the natural chunk height (256 blocks), and sit at the bottom of the farm (in the same chunk) more than 80 blocks below it (more than 5 chunks vertically speaking), will mobs cease to spawn even though I am legally still in the same chunk and within mob spawn range (128 blocks), or does the server's "chunks to load" distance stop mobs from spawning more than 80 blocks away (vertically speaking)?

I'm asking because I have read a lot of articles on reddit and other sites where view distance does seem to affect mob spawn rates, and to get maximum spawn rates the view distance on a single player world has to be 16 chunks minimum (even for a vertical "same chunk" grinder). This is a much higher view distance than the server has implemented and I am wondering if I am wasting my time building this farm since the build exceeds the 5 chunk limit (vertically) and has an automatic redstone clock system that will need to remain running while I am more than 80 blocks below it (to flush the mobs and grind them).

And one last thing. From my understanding, the view distance may not be the same as the loaded chunk area. For example, I can have my view distance cranked up and still see chunks I have traveled through even though they are outside of the 5 chunks currently loaded by the server, but the chunks really won't be loaded server side, meaning all redstone systems or mob spawns are stopped until I am back within the 5 chunk range even though I can still see the landscape in that area. Is this true?

I hope this all makes sense and thanks in advance for any answers.

Chunks are 16x256x16 so you don't have to worry about the vertical axis for chunk loading. However you do need to worry about the vertical axis for mob spawning.

Thanks for the answer Pand. Good to know I haven't been wasting my time

Are you trying to make a spawnerless overworld mob grinder?

wait then how does the iron farm spawn iron golems? Those things are huge. on a y axis?

@RebelGamer101 Thanks for the answer Pand. Good to know I haven't been wasting my time

It's very unlikely that any kind of spawnerless mob grinder is going to work properly unless you have a very good handle on game mechanics. So you very well may be wasting your time.

@BoneChi11er wait then how does the iron farm spawn iron golems? Those things are huge. on a y axis?

I have no idea what you are trying to ask, but here's more information on the topic:
http://minecraft.gamepedia.com/Tutorials/Village_mechanics

@pand1024 Are you trying to make a spawnerless overworld mob grinder?

Yes. Apparently this doesn't work on SMP. Nothing spawns in it. Few mobs here and there, but nothing like it would be on single player. Gigantic waste of time, but at least I can turn it into storage or something.

@BoneChi11er wait then how does the iron farm spawn iron golems? Those things are huge. on a y axis?

Iron farms spawn golems based on the number of villages and village size. You can create your own village from scratch. Some pretty complex mechanics behind making an extremely efficient one. YouTube has some good tuts for iron farms. Regular mob grinders don't seem to work with a lot of people on though. From my understanding, the mob limit cap is increased by extra players, but this seems to not be the case. The more players means less spawns in practice, even if the formula in the code says otherwise.

@pand1024 It's very unlikely that any kind of spawnerless mob grinder is going to work properly unless you have a very good handle on game mechanics. So you very well may be wasting your time.

I thought I had a handle on the mechanics, but apparently I was wrong. I built in the middle of a giant deep ocean biome at near build height limit and I'm still working on lighting up all of the caves underneath, but so far no real luck in getting spawns in the grinder. I forget the formula now but apparently there is a mob spawn cap within a given Minecraft world. This cap is increased for each player on a server according to the wiki article I read.

However, this doesn't seem to be the case. The mob spawn rate is much lower than I expected it to be. I didn't expect a ton of spawns, but a few every minute while I AFKed would have been better than nothing. In two days while putting on the final touches, there has been one skeleton and one spider spawn in the grinder. That's it.

@RebelGamer101 I'm still working on lighting up all of the caves underneath

Even if you light them all up that won't solve your problem. You really do need to get rid of every spawn-able space to get good rates, and that includes slimes that spawn regardless of the lighting.

Mobs spawns aren't just capped the rate decreases dramatically even if you are half way to the cap.
Also there may be issues with mobs spawning above 126, I'm not really sure.

I'm going to make an attempt to clarify on some points here, in the hope that anyone else asking these questions will find this useful.

Mob Caps
All mobs are spawned up to a certain cap. In a single player unmodified game the hostile mob cap is 70. On multilayer servers the mob cap is dependant on the number of chunks loaded according to the formula:

cap = chunks / 289 * 70

The mob cap is shared between all players.
On CM chunks are loaded around the player with a radius of apparently 5 (although I suspect this may have been changed recently to 3 or 4), giving 100 loaded chunks total. As an example; with 20 players online the hostile mob cap would be approx. 484.

Interestingly this also means that if 1 player has 484 hostile mobs around them, no mobs will spawn for other players unless one despawns!

Hostile mob spawning

Each tick the game checks if the mob is met, if not it will attempt to spawn up to the mob cap. The game will randomly check for spawnable blocks (i.e. opaque, low light etc.) and spawn mobs on these as they're found. Notably on severs these spawns could happen for any player.
One consequence of this is that players with more spawnable blocks around them will be more likely to have more hostile mobs spawn around them. This considerably reduces the spawn rates at spawners since spawners generally have relatively few spawnable blocks compared with a random spot on the ground at night.

Mobs spawns aren't just capped the rate decreases dramatically even if you are half way to the cap.

I'm not sure where you got this from but I don't think that this is true, and I cannot see a reason for it.

Mob farms at the build height and vertical distance

Hostile mobs will instantly despawn if there is no player within 128 blocks. However it's important to note that they can still spawn over 128 blocks away. For the horizontal axes this is irrelevant on CM since mobs beyond 80 blocks from a player are unloaded. Vertically however it will still occur.
As pand1024 said chunks go from y=0 to y=258. This is why mob spawners work best when built at the hight limit. Building over an ocean and lighting up caves below etc. will increase spawn rates, but not by very much since any mobs spawned there will instantly despawn if the player is up at the build height.

Hopefully this all makes some sort of sense and is even remotely useful to anybody
XD

Render distance was 4 last I heard. This page gives a lot of information on spawn mechanics, but doesn't include some bugs that can also have a big effect.
http://minecraft.gamepedia.com/Spawn

All of this has been helpful. Thanks for all the contributions. SO, it seems that the simple dark room mob grinders aren't going to be that efficient or even work at all when multiple players are online at once. But what if:

I built a gigantic grinder. Let's take a nether grinder as an example since light levels won't matter. I build a 30x30 platform at level 220 on the nether roof and I build, from an epicenter, one in every possible chunk that can be loaded around this epicenter. Basically 4 chunks (roughly 2 platforms) in every direction. This would give me maximum spawn capabilities since there would be a flat area of opaque blocks extending for four chunks in every direction from the epicenter. I would be high enough above the spawnable regions below me so nothing would be spawning there.

I could even stack the platforms a few times to create even more spawn points. In theory, this seems like it would create a perfect environment for spawns on SMP. It also seems like, in theory, that a setup like this could possibly steal most mob spawns from the rest of the SMP world if it got going (maybe at a down time when most players are asleep).

I'm curious to know what others think about this idea and if it would be a feasible solution to the dark room grinders on SMP? The same concept could be applied to overworld grinders, although any grinder like this would be a massive build and take a lot of time (overworld grinders would also require a shit ton more resources).

The only problem I see with a nether grinder is having golems as the grinders since all movement would stop before reaching the end of the render space at around 32 blocks away, even though the render space is double that. Is the same distance also true for redstone contraptions such as a piston grinder? I guess one solution would be to ride a minecart back and forth through the areas to have the golems and hostile mobs move, but this would also cause chunks to constantly unload and reload and really kill the efficiency I am trying to achieve.

I enjoy doing builds like this on single player and it would be great if I could get one to work on multiplayer.

If you want a good test to see if your idea will work. Open a single player world set the the render distance to 4. Quickly mockup the most basic version using /fill and /clone. If it works theres a good chance it will work on the server.

@pand1024 If you want a good test to see if your idea will work. Open a single player world set the the render distance to 4. Quickly mockup the most basic version using /fill and /clone. If it works theres a good chance it will work on the server.

This is great way to test if there is any problems with the grinder!

TL;DR

You're right, the bigger the spawning area the more spawns you'll get. The problem with the idea of 'stealing' mob spawns from other players is that you'll be killing all your pigmen very quickly, but other players probably won't be killing hostile mobs around them as fast. I think this means your farm will slow down over time (not 100% sure about this).

Regarding the server render distance and redstone/mobs: Redstone contraptions keep running as long as they are within the loaded chunks.
However in minecraft there are two different types of loaded chunks; fully loaded and lazy chunks. Fully loaded chunks process everything, lazy chunks don't process entites. For CM as far as I can tell the first three chunks out from the player (including the one you're in) seem to be fully loaded, and the forth is lazy. You probably don't want the farm running into lazy chunks to avoid the need for chunk loading.

The iron golems should still attack the pigmen when you're further than 32 blocks away as long as they're not in lazy chunks (might want to test this - I'm not sure).

Also in case you're not aware I think there's an issue with the iron golem pigman farm. Pigmen can occasionally summon regular zombies as reinforcements, which will attack the golems. The golems will slowly die - this does take a while though.

@pand1024 If you want a good test to see if your idea will work. Open a single player world set the the render distance to 4. Quickly mockup the most basic version using /fill and /clone. If it works theres a good chance it will work on the server.

The builds I'm planning work great in single player. Good idea about testing with render distance down though.

@NutjobBob This is great way to test if there is any problems with the grinder!

TL;DR

You're right, the bigger the spawning area the more spawns you'll get. The problem with the idea of 'stealing' mob spawns from other players is that you'll be killing all your pigmen very quickly, but other players probably won't be killing hostile mobs around them as fast. I think this means your farm will slow down over time (not 100% sure about this).

This would actually be ideal if it works. My goal isn't to hog all the mob spawns. So if it degenerated over time that would be fine if I had an initial burst of production. I have seen mixed articles about how this would work. Some say it can consume all spawns in the world once it got running and others say it will degenerate over time and the chunks will need to be reloaded to get it going again.

I know from my guardian farm over a year ago back in 1.8, the guardians seemed to work like a physical spawner. I could let the guardians build up no matter what and it would consume the mob cap very quickly. It took it nearly 30 minutes to get started though, but it seemed to not degenerate but "regenerate" over time and become more and more efficient as long as I was in range. Dark room spawning seems to work in reverse though, but I still need to test it.

I've built one overworld dark room spawner so far and it was useless. I'm hoping to have better luck in the nether. Unfortunately, I may end up just having to use physical spawners (which I already have two of, spiders and skeletons). A nether spawner would be great for ghast tears and magma cream though.

At the section of the nether I'm in, I'm also over top of a fortress which always has a ton of mobs in it. Hoping the same it true for that entire area of chunks and building spawn pads at build limit here will keep that same rhythm.

Regarding the server render distance and redstone/mobs: Redstone contraptions keep running as long as they are within the loaded chunks.
However in minecraft there are two different types of loaded chunks; fully loaded and lazy chunks. Fully loaded chunks process everything, lazy chunks don't process entites. For CM as far as I can tell the first three chunks out from the player (including the one you're in) seem to be fully loaded, and the forth is lazy. You probably don't want the farm running into lazy chunks to avoid the need for chunk loading.

I noticed this too about the lazy chunk distance. Skeletons and zombies will be rendered but not moving and won't burn in the light til you are within range of them to move, which proves the four chunks loaded instead of five as they seem to disappear at five and don't burn til they are within three.

The iron golems should still attack the pigmen when you're further than 32 blocks away as long as they're not in lazy chunks (might want to test this - I'm not sure).

Also in case you're not aware I think there's an issue with the iron golem pigman farm. Pigmen can occasionally summon regular zombies as reinforcements, which will attack the golems. The golems will slowly die - this does take a while though.

I don't mind the golems dying over time. I like to build things and I like to keep them maintained. That's the joy of MC for me :). The farm would be more for ghast tears and magma anyway since I have trouble finding magma in normal travel. Since I'm over a fortress, I was hoping for wither skeletons to spawn as well, but not sure that is how they work. I haven't read up on the mechanics regarding how they spawn yet and what conditions have to be met. It may be as simple as building the spawn pads out of nether brick in the fortress chunks, I dunno.

I've got one pad built so far though and no spawns yet. I will build it to the render distance from a center pad and see how it goes. May be a waste of time, but I guess testing gives me some incentive. Just so I know for sure.

Thanks for the input.

I know from my guardian farm over a year ago back in 1.8, the guardians seemed to work like a physical spawner. I could let the guardians build up no matter what and it would consume the mob cap very quickly. It took it nearly 30 minutes to get started though

Yeah, the guardian spawns will be a bit different because the number of spawnable blocks are so much higher. Since they just need a water block the area around a monument has over 70,000 blocks they can spawn in if they're all water. The game only checks the mob caps at the beginning of each spawning cycle, so the cap can be massively exceeded if there's lots of spawnable blocks around. This happens noticeably with guardians and squid, I had over 200 guardians spawn in a couple of ticks the other day!
Obviously the same is true for any other mob if you make the spawn area big enough - it's just a ton of work.

Since I'm over a fortress, I was hoping for wither skeletons to spawn as well, but not sure that is how they work. I haven't read up on the mechanics regarding how they spawn yet and what conditions have to be met. It may be as simple as building the spawn pads out of nether brick in the fortress chunks, I dunno.

Sadly they don't work like that.
Check out these videos for more info (they're both the same, but 1 says 1.9 in the title so you know it's legit):
https://www.youtube.com/watch?v=RcQzqk_8OTo
https://www.youtube.com/watch?v=PJLJ5fynNGw

I noticed this too about the lazy chunk distance. Skeletons and zombies will be rendered but not moving and won't burn in the light til you are within range of them to move,

A fun (and possibly useful) way to show this is to put a block of sand on a regular piston and attach it to a clock. Walk away while the clock is running. When you're far enough away that the sand is in a lazy chunk instead of appearing to fall when the piston depowers the sand will teleport 1 block down. If you use red sand it will magically turn into normal sand :)