As Sorontar said, I posted in general because we had PMed the person involved - so this post was not to do with them - but we wanted to try and make people aware of the fact that stuff left going can cause lag.
It was me and simply inexperience as I've only been playing minecraft for just over a week.
Thank you OJ
It's just one of those things, and hopefully we can work out what went wrong and stop it happening again (for anyone)
Never any lag when I was on with all my stuff running for a hours and hours, so it could easily have been the water as that's the only thing that 'changed' from my previous quarry setups?
Apparently it was fine earlier in the evening (I think someone said you were last on 7pm?) - so whatever it was, seems to have happened somewhere around 8-9pm.
Can we get some info on exactly what was wrong other than the quarry or is it hard to pinpoint? I mean if it's for example a case of pipe overflowing or such, then there are steps the rest of us can take to prevent that from happening in our own bases.
The problem is - we don't really know for sure what caused it. I don't think you can quite appreciate the situation.
Whilst in the lag zone, I had 1 frame every 5 seconds! Some were luckier with slightly better than that. Movement at all was *****incredibly****** difficult.
When we discovered the problem we had to get into the area (far more difficult than it sounds) which involved holding down the forward key and waiting while you laggily inched forward. It took probably at least half an hour just to walk into the effected area from where the lag started (lag started as soon as the chunk loaded in view). Even with all the graphics and render distance set low.
Then we had to try to get into the place and try to see what the problem was, and what we could do to fix it. But given it was difficult to even look around (you had to guess how far to move your mouse then wait a few seconds to see if you've looked in the direction you planned to, or if you went too far and turned yourself around), and difficult to move around - we had to just do our best to look around and try to shut off what we could, hoping it would eventually reduce the lag. We were not able to stand around discussing the merits of design or anything - we needed to do whatever we could to try and get the server back, and we needed to do it as quickly as we could - so other players wouldn't get stuck.
Even with restarting the server a few times, and logging in/out to gain a few extra seconds of movement before getting locked up again... it took hours just to move around.
Because of the lag, the "clean up crew"
were put into creative mode - partially so no harm came to us - but also to prevent harm to any buildings (though the entire server was so laggy at that point, the mobs were themselves barely moving). We ended up having to remove switches rather than turn them off - because the lag made switching them very difficult.
It was seriously an horrific situation.
The water from the quarry was the most obvious - as it was flowing from above ground level down to bedrock, and a lot of running water can cause lag. But it's unlikely that it alone was the cause of the problem, as normally that amount of water would not cause such game-breaking lag. It probably was just the "straw that broke the camel's back" so to speak.
There was 1 source block a few blocks up from the remaining "pool" of water, which we managed to remove, but then it seemed the "pool" (which was floating up in the air) was comprised of a few source blocks. So we had to try and stop those, to let the water drain down. It may have been the lag causing it, we don't know, but as the water dropped, it seemed it was creating new source blocks as it dropped. So we kept having to remove those to get the water to drain. Once we'd gone down a good way - the lag improved slightly and the water started to drain properly. As it drained, the lag eased and once the water was gone, the lag vanished also.
I believe someone else noticed a lot of blocks lying around - presumably dropped from overflowing pipes or something - which was thought to also contribute to lag. (It was impossible to do anything about picking those up and doing anything with them, but they would have disappeared eventually - reducing any lag they caused) Someone else mentioned that there was automatic sorting happening, which is believed to also cause some lag.
What ultimately caused it - we don't know. It was probably just a combination of things..
2) Does stationary water have the same impact, say, if I mined a 64x64 quarry then filled it to the top of stationary water? (NOT flowing water).
Definitely not, because stationary water at the top becomes falling water in all blocks below it :P (unless you actually filled every single block from bedrock to ground level with water, which would be insane and take forever)
Water itself shouldn't be too much of an issue, but water in addition to other lag-inducing things, probably is.