I've followed three online courses. One I completed and did all the assignments. Two where I watched all the material but did not attempt the assignments (one required I rigged up a video camera to submit; could not be bothered).

Quite frankly, I got what I wanted out of these courses. So how is this a failure?

I have to balance effort with other commitments. I trust I am not the only one. Signing up is cheap. I've signed up for a few more but other real life took precedent. No big deal.

On the other hand, I don't see online courses replacing traditional educational settings but that was pretty naive to being with.

So: nothing to see here. Yawn!

It's still an interesting article. It seems they've found a way of cheaply producing ammonia from hydrogen. Not sure they meant ammonia exactly, but they mention "liquid-based inorganic fuel" and later talk about how ammonia is important for fertilizer, so I'm kinda guessing that's what they're making. Ammonia can then be used to either make fertilizer, liquid fuel substitutes and a bunch of other interesting processes.

I teach physics. The most depressing part of my job is teaching a general-education class where I have to explain global warming.

Scientists don't have a private agenda. We would LOVE to be wrong about this, but:
- Temperatures are going up worldwide
- Global temperatures are historically very well correlated to CO2 concentrations
- CO2 concentrations have a straightforward and well-understood effect on infrared light produced by
earth's blackbody radiation
- Even small changes to global temperature will create big changes to local climates
- We can stop this, but only if radical action is taken right now
so
- We're all fucked.

This is not the time for the debate about whether the effect is real. This is the time for debate about just how MUCH we should be panicking. We're in the deep shit here. We're talking about large proportions of humanity not having enough food to eat. The resulting warfare and hardship will be devastating.

In that respect, that is correct, the increase might indeed be just noise.

This data is pretty hard to come by, I agree, so I had to make some assumptions (elaborated below). Can you cite your sources?

While it is true that some efficiency offsets might be made, your numbers simply do not add up to the graph Dunkelfalke linked. It lists lignite at 3201 TJ in 1990 and 1645 TJ in 2012. That is not "[usage] of brown coal is still nearly 20% below the 1990 level (in primary energy)", that is a 50% reduction in primary energy. All of that also happened before the year 2000 - since then, pretty much no reduction in lignite use has occurred. If powerplant efficiency were indeed rising while electrical generation remained mostly flat during the 2000-2011 period, that would imply that a rising proportion of that input lignite energy (which flatlined during that time period too) is being used for heating and other uses. However that doesn't appear to be the case either (coal use outside of electricity is falling rapidly) - this leads me to believe that there hasn't been such a dramatic increase in efficiency as to be able to confidently say that the recent increase in generation is due to an increase in powerplant efficiency. Also, how can you claim use in electrical generation is 10% below 1990, when even you said yourself just a few moments before that "no one can deduce how much more brown coal was used for that". I'd really appreciate if you could cite your sources, that would allow us to clear up the situation. If you have access to figures on lignite consumption by coal fired power plants, that would be great. Otherwise, the only reliable thing we can say is that electrical generation from lignite is at an all time high since 1990.

Maybe you should start with your own advice. The poster was referring to electrical generation here, not overall energy use. Your graph is for overall energy use (and I'm not sure about the proportions there either, they seem a bit off). You might have been clued into that by the units being petajoules (customarily used for overall energy production) not watthours (customarily used for electrical generation). Another thing that might have ticked you off is that mineral oil is a good 1/3 the energy share there. And natural gas about 1/4. In actual fact, when you look at the right graphs, in electrical generation, oil accounts for a meager 1% and gas about 11%. In relative proportions lignite has remained mostly stable since 1990, however in absolutes, 2013 (161 TWh) was indeed a record year since 1990 (171 TWh). Hard coal has also picked up in the last 5 years.

I think you misunderstood my reply. I was replying to the poster talking about iSCSI having to be implemented in ZFS. That's what I was addressing.
You talk about a different thing altogether - ZFS backing. The zvol-on-another-zpool solution should work, although performance will suck. The zvol-on-the-same-zpool solution can and will hang for obvious reasons.

I was talking about iSCSI support, not how the ZFS themselves pools are built. Yes, ZFS *does* prefer raw disk backing (due to certain management simplifications), but it does not need it. In fact, it's quite possible and people do frequently run ZFS on top of RAID arrays.

I've confirmed it by actually reading the source code. Even a quick look at the manpage will tell you the same:

Keep perspective. Are you really going to build a box like that with just one 2 GHz quad-core CPU?
I have pushed 4GB/s through a SAS SSD array on ZFS, but even so I maxed out on other stuff way before the CPU and much less checksumming ever began to be an issue (e.g. had to go through two LSI SAS 9200-8e HBAs, because one maxes out the PCI-e 2.0 x8 lanes; with two HBAs I maxed out on the two 6G SAS links to my JBOD). That the point of my post. I've yet to see a system which is constrained by the checksumming in any meaningful way.

Sun still had closed bits in the OS kernel when OpenSolaris was CDDL'd, so GPL was a non-starter because of GPL's "infectious" nature of spreading to all source that makes up a project. CDDL is more permissive in this - it simply forces you to keep the free bits that you got free, but doesn't expand to anything outside of the source files you got.

iSCSI doesn't need to be baked into ZFS, in fact, even on Illumos it isn't. It's in a completely different subsystem and will happily work with any block device as its backend storage (be it a physical drive, a ZFS zvol, a loopback block device or anything else, really).

You can thank your package maintainer for this. ZFS never ever ever upgrades the on-disk format silently. You always have to do a manual "zpool upgrade" to do it. It'll tell you when a pool's format is out of date in "zpool status", but it'll never do the upgrade by itself.

Again, this is not ZFS' fault, it's your package maintainer for auto-upgrading all your imported zpools. ZFS never does this by itself.

The overhead is barely there at all. I've measured the performance of the default fletcher4 checksum on a modest 2GHz Core 2 CPU and it comes to around 4GB/s/core. Now given that most CPUs now come with 4 or more cores, in order to get the checksum to be 10% of CPU overhead, you'd have to do be doing around 1.2GB/s of I/O. Needless to say, you're not ever going to get that even for fairly high-performance boxes.

What answer? You gave a few links to wikipedia with zero analysis to support it. You claim shit like "obviously we can get some energy back from the steam turbines too" without actually knowing and showing that doing so is feasible.
Look, it's really simple. Give your best case analysis for what you propose to do. No links to wikipedia and vague statements like "seems your main technical objection is being worked out with a 780 KW beam for spallation". Tell me exactly how you propose this to be done and how that adds up quantitatively. How much power, in what accelerators, how much would such a system cost and how would you propose we construct it. No more evading. Talk to the point.