Interesting although I'd have liked more summaries: there's an awful lot there.
But the reasons I choose filesystems are more about reliability, failure modes, surrounding tooling, and so on.
Btrfs fails in several critical areas:
1. No way to accurately find free space
2. catastrophic failure on write if a volume fills up, the probability of which is greater because of #1
3. repair tools usually do not recover a corrupted volume and in my testing are most likely to render as damaged volume completely unreadable, which makes #2 worse
Put these things together and I can never trust Btrfs again. In the 9 years since I encountered these, I see no effort to fix them, just fooling around witg unimportant side details like performance tweaks.
Fix the critical issues first then make it faster.
This. Btrfs blew up without ANY reason at all in my case. Rebooted and the system won't even recognize any filesystem. All btrfs tools fails to recover a single file.
I've had a ZFS array running since ~2009. It's gone through upgrades and disk replacements, etc. Have not suffered a data loss in that time. ZFS I'd the goat.
I used ZFS until it self-corrupted and refused to mount rw ever again. Community support was totally unhelpful and there was no resolution except buy another array and use something else. There's way too much ZFS cult fanboy glazing out there it doesn't deserve.
It's hard to show with any accuracy how likely a filesystem is to not break when the SHTF or something weird happens, or if they've handled all the weird corner cases, with any kind of automated test.
For that you have to dig into the methodology, look at the code, look at user reports, etc.
But you can get a pretty good approximation just from the philosophies and attitudes of the engineers and what they're talking about.
The talk I just gave at the Rust for Linux conference was all about that - how do we make the system debugable, the community aspect of how we respond to bug reports and talk to users, the prep work for the Rust conversion and formal verification and how we're approaching all that.
Reliability doesn't come out of nowhere, "all bugs are shallow with enough eyeballs" really doesn't apply to filesystems. You just have to plan for it, come up with a methodology, and do the work.
It's not materially better now. The devs are in denial about the problems because lots of big users are saying "works fine on my machine."
Sure, if you have lots of backups, if you have huge volumes on huge disks and they never fill up...
But it's the default in Fedora, Spiral Linux, Garuda Linux, siduction and others. Personal distros for people's own PCs and those are not well-supported enterprise kit.
SUSE takes snapshots before packages are installed. The package manager cannot tell if the disk will fill up as a result because on Btrfs the `df` command lies.
If its Btrfs root fills up and the OS writes to it, it 100% will self-destruct, and the `btrfs-repair` tool (`fsck` replacement) cannot fix drives and usually makes the corruption worse and renders the drive unreadable.
This is why in the earlier thread about swapfiles...
... I advised 2 commenters not to recommend keeping the OS and data in a single big volume. I got downvoted for it. I was rude. Well, I was, but I stand by my comments even though I'm sorry for my tone when I made them.
> What is the difference between cilia and flagella?
Broadly and generally:
• cilia come in large groups, in rows or in sheets; flagella come singly or in pairs (occasionally more)
• cilia are short, and they beat backwards and forwards in a coordinated way, like a Mexican wave; flagellae are long, and in prokaryotes, they spin around their axis.
(Eukaryote flagella -- e.g. spermatozoan "tails" -- are a different structure that just resembles the ones in prokaryotes. Prokaryotes are bacteria and archaea -- no cell nucleus. Eukaryotas have cell nuclei and other organelles, such as mitochondria and chloroplasts. Their flagellae bend and flap, they don't spin.)
Take 1 cell. Can you count the moving hair things? Then they're flagella. Is the beastie covered in lots of them, countless, like fur? Then they're cilia.
I read earlier this year about Berg's and Samuel et al.'s (and maybe others') amazing flagellar motor discoveries. I didn't realize they were only prokaryotes; the motor seems like a sophisticated mechanism.
The "Venus's girdle" is a long thin flat belt-shaped thing, but it is not wormlike. It has no head, no sense organs or anything, and the "mouth" and other main organs are in the centre of the belt, not at one end like a worm or a snake -- or you.
Most ctenophores are called "comb jellies"; one group is named "sea grapes". They are hard to generalise and not all are like this by any means, but most tend to be small, and egg-shaped, possibly with protrusions. Most tend to have 2 long trailing tentacles they use to catch food.
Most don't have muscles. They swim using bands of cilia,which are the same fine hairs that unicellular organisms use to swim, and that line your bronchi and throat. Your body uses cilia to propel mucus out of your lungs and up to where you can cough it up.
Comb jellies' cilia are in long lines, usually 8 rows. They move like a Mexican wave in a sports crowd. The light refracting through these near-microscopic beating hairs looks like they flicker with rainbows. Thus the name, comb jellies. They are often radially symmetrical along the line from mouth to other end.
That's all they have; no legs, no fins, no eyes, no dedicated sense organs. Most are not bioluminescent, but like I said, there's pretty much nothing you can say about comb jellies that applies to all of them. One type is an internal parasite that looks like a worm, although internally it's nothing like a worm. (That one is not 2-way symmetrical like us and most animals; it's four way symmetrical. It is alien compared to all other wormlike things.) Other parasitic ones are just small branching bags that don't move.
They are about the only multicellular animal that swims with cilia. They are so unlike all other multicellular animals it's just about possible that they evolved the whole plan of being multicellular entirely independently.
They look like jellyfish but are nothing like them.
Jellyfish have lots of tentacles; those comb jellies that have them, have 2, no more, no less. The tentacles don't sting; they are sticky, and the animal catches tiny plankton this way and pulls them up to its mouth to eat.
One type, Beroids, have a mouth they can close, and they can actually swallow other smaller jellies (comb jellies or jellyfish). Their lips zip shut from the edges and they have more cilia inside to propel the prey down their "throat," but they can't chew.
Some have muscles and can flex and move. Some but not many sort of swim this way, like the Venus's girdle. A very few stick to the bottom and stay there.
Comb jellies tend to have a front end and a back end, but most have no anus, just 1 hole; any food waste is vomited. But, rather wonderfully, some form an anus only when they need to poop and then it closes up again, "heals" shut, totally gone.
They are not really alien; their genetic code is the same as ours, although they don't do things all other animals do. For example their nerves do not have synapses, so they don't need neurotransmitters to carry signals across the joins between nerves. They don't have joins. Their nerves are a continuous mesh, with long lines of cytoplasm dotted with nuclei, not divided up into separate cells -- the same sort of structure as most fungi, but flexible.
I think they are beautiful. Little was known about them when I did my biology degree, but I got into them about 5 years ago and read a lot about them for a while. They are like nothing else. Even the parasitic ones, while kind of nasty, are deeply weird.
https://news.ycombinator.com/item?id=49727434
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