I've recently switched my FreeBSD setups to use that scheme, and it's been nice. Would be interested to hear if it's similarly straightforward on Debian (my second-favorite OS :)
Obviously requires support in the bootcode; I'm not sure of the state of that for Linux.
While I can't comment on using it for root, I can say for other use, the only annoyance I have is compiling the kernel module on every single update. This is automatically handled by APT, but for very small servers it can be slow... at most ~15 mins. Could be solved with private distribution for a large fleet but I can't be bother with that stuff. Hoping at some point Debian will relax their strict "to the letter of the GPL" attitude at some point like they did with install media drivers. But it's not the worst experience, at least installing is automated.
Also nice way to recover zfs if anything goes wrong. yea, it's a linux image for just booting. But you put it as an EFI image, and works great.
- bootloader (when root is on ZFS)*
- ARC vs kernel page cache and OOM Killer
That's all in my opinion.
*: Relative to FreeBSD, but that's because bootloader in FreeBSD is part of the base system and in linux it could be one of many.
The only issue I've had with the kernel module aspect is VPS configuration, I use Linode and they used to automatically set everything to use the hypervisor kernel, but the kernel module is obviously built against the versions installed on your OS and these will probably be different.
All you have to do is make sure the boot configuration is set to use GRUB if using a VPS. Linode seem to have switched to this by default for Debian now.
Though Linux support a decade ago with ZFS was pretty rough around the edges. That's not true anymore for many distros of Linux.
