The main hurdle is hostile Linux kernel developers who aren't held accountable intentionally breaking ZFS for their own petty ideological reasons e.g. removing the in-kernel FPU/SIMD register save/restore API and replacing it with a "new" API to do the the same.
What's "new" about the "new" API? Its symbols are GPL2 only to deny it's use to non-GPL2 modules (like ZFS). Guess that's an easy way to make sure that BTRFS is faster than ZFS or set yourself up as the (to be) injured party.
Of course a reimplementation of the old API in terms of the new is an evil "GPL condom" violating the kernel license right? Why can't you see ZFS's CDDL2 license is the real problem here for being the wrong flavour of copyleft license. Way to claim the moral high ground you short-sighted, bigoted pricks. sigh
From my point of view it is a real usability issue.
zfs modules are not in the official repos. You either have to compile it on each machine or use unofficial repos, which is not exactly ideal and can break things if those repos are not up to date. And I guess it also needs some additional steps for secureboot setup on some distros?
I really want to try zfs because btrfs has some issues with RAID5 and RAID6 (it is not recommended so I don't use it) but I am not sure I want to risk the overall system stability, I would not want to end up in a situation where my machines don't boot and I have to fix it manually.
I have been using ZFS on Mint and Alpine Linux for years for all drives (including root) and have never had an issue. It's been fantastic and is super fast. My linux/zfs laptop loads games much faster than an identical machine running Windows.
I have never had data corruption issues with ZFS, but I have had both xfs and ext4 destroy entire discs.
Why are you considering raid5/6? Are you considering building a large storage array? If the data will fit comfortably (50-60% utilization) on one drive, all you need is raid1. Btrfs is fine for raid1 (raid1c3 for extra redundancy); it might have hidden bugs, but no filesystem is immune from those; zfs had a data loss bug (it was rare, but it happened) a year ago.
Why use zfs for a boot partition? Unless you're using every disk mounting point and nvme slot for a single large raid array, you can use a cheap 512GB nvme drive or old spare 2.5" ssd for the boot volume. Or two, in btrfs raid1 if you absolutely must... but do you even need redundancy or datasum (which can hurt performance) to protect OS files? Do you really care if static package files get corrupted? Those are easily reinstalled, and modern quality brand SSDs are quite reliable.
I am already using ext4 for /boot and / on nvme, and I am happy with that.
I want to use raid 5 for the large storage mount point that holds non-OS files. I want both space and redundancy. Currently I have several separate raid1 btrfs mounts since it is recommended against raid5.
It is a problem because most of the internal kernel APIs are GPL-only, which limit the abilities of the ZFS module. It is a common source of argument between the Linux guys and the ZFS on Linux guys.
The reason for this is not just to piss off non-GPL module developers. GPL-only internal APIs are subject to change without notice, even more so than the rest of the kernel. And because the licence may not allow the Linux kernel developers to make the necessary changes to the module when it happens, there is a good chance it breaks without warning.
And even with that, all internal APIs may change, it is just a bit less likely than for the GPL-only ones, and because ZFS on Linux is a separate module, there is no guarantee for it to not break with successive Linux versions, in fact, it is more like a guarantee that it will break.
Linux is proudly monolithic, and as constantly evolving a monolithic kernel, developers need to have control over the entire project. It is also community-driven. Combined, you need rules to have the community work together, or everything will break down, and that's what the GPL is for.
I remember it being a pain in the ass on Fedora which tracks closely to mainline. Frequently a new kernel version would come out that zfs module didn't support so you'd have to downgrade and hold back the package until support was added.
Fedora packages zfs-fuse. I think some distros have arrangements to make sure kernels have zfs support. It may be less of a headache on those
The main hurdle is hostile Linux kernel developers who aren't held accountable intentionally breaking ZFS for their own petty ideological reasons e.g. removing the in-kernel FPU/SIMD register save/restore API and replacing it with a "new" API to do the the same.
What's "new" about the "new" API? Its symbols are GPL2 only to deny it's use to non-GPL2 modules (like ZFS). Guess that's an easy way to make sure that BTRFS is faster than ZFS or set yourself up as the (to be) injured party.
Of course a reimplementation of the old API in terms of the new is an evil "GPL condom" violating the kernel license right? Why can't you see ZFS's CDDL2 license is the real problem here for being the wrong flavour of copyleft license. Way to claim the moral high ground you short-sighted, bigoted pricks. sigh
From my point of view it is a real usability issue.
zfs modules are not in the official repos. You either have to compile it on each machine or use unofficial repos, which is not exactly ideal and can break things if those repos are not up to date. And I guess it also needs some additional steps for secureboot setup on some distros?
I really want to try zfs because btrfs has some issues with RAID5 and RAID6 (it is not recommended so I don't use it) but I am not sure I want to risk the overall system stability, I would not want to end up in a situation where my machines don't boot and I have to fix it manually.
I have been using ZFS on Mint and Alpine Linux for years for all drives (including root) and have never had an issue. It's been fantastic and is super fast. My linux/zfs laptop loads games much faster than an identical machine running Windows.
I have never had data corruption issues with ZFS, but I have had both xfs and ext4 destroy entire discs.
Why are you considering raid5/6? Are you considering building a large storage array? If the data will fit comfortably (50-60% utilization) on one drive, all you need is raid1. Btrfs is fine for raid1 (raid1c3 for extra redundancy); it might have hidden bugs, but no filesystem is immune from those; zfs had a data loss bug (it was rare, but it happened) a year ago.
Why use zfs for a boot partition? Unless you're using every disk mounting point and nvme slot for a single large raid array, you can use a cheap 512GB nvme drive or old spare 2.5" ssd for the boot volume. Or two, in btrfs raid1 if you absolutely must... but do you even need redundancy or datasum (which can hurt performance) to protect OS files? Do you really care if static package files get corrupted? Those are easily reinstalled, and modern quality brand SSDs are quite reliable.
I am already using ext4 for /boot and / on nvme, and I am happy with that.
I want to use raid 5 for the large storage mount point that holds non-OS files. I want both space and redundancy. Currently I have several separate raid1 btrfs mounts since it is recommended against raid5.
It is a problem because most of the internal kernel APIs are GPL-only, which limit the abilities of the ZFS module. It is a common source of argument between the Linux guys and the ZFS on Linux guys.
The reason for this is not just to piss off non-GPL module developers. GPL-only internal APIs are subject to change without notice, even more so than the rest of the kernel. And because the licence may not allow the Linux kernel developers to make the necessary changes to the module when it happens, there is a good chance it breaks without warning.
And even with that, all internal APIs may change, it is just a bit less likely than for the GPL-only ones, and because ZFS on Linux is a separate module, there is no guarantee for it to not break with successive Linux versions, in fact, it is more like a guarantee that it will break.
Linux is proudly monolithic, and as constantly evolving a monolithic kernel, developers need to have control over the entire project. It is also community-driven. Combined, you need rules to have the community work together, or everything will break down, and that's what the GPL is for.
I remember it being a pain in the ass on Fedora which tracks closely to mainline. Frequently a new kernel version would come out that zfs module didn't support so you'd have to downgrade and hold back the package until support was added.
Fedora packages zfs-fuse. I think some distros have arrangements to make sure kernels have zfs support. It may be less of a headache on those
In tree fs don't break that way