COW and volume management?

> Maybe you could find and list at least one flaw?

i've used ZoL on several machines for over a decade now. i've also written a large disk-management tool that has had to support all variety of filesystems. i've encountered zero problems with it from a user, despite generally running tip-of-git checkouts with most features enabled. can't say enough good about it from that perspective.

as an app writer and administrator, it has some annoying issues. it lives outside the standard filesystem management (fstab / systemd mount objects) with its own systemd services. i'm still unsure what exactly zed does, or what a ZEDLET is, or why it's written ZEDLET. you won't find the zpools in /sys/block, nor in /proc/diskstats, meaning you won't find them in say iostat, nor in blkid. compiling against libzfs is a shifting and rewardless PITA due to libspl clashing with all manner of userspace entities (random.h last i checked), and the OpenZFS developers have explicitly declared that one ought not compile against libzfs, essentially limiting sane userspace to the OpenZFS toolset.

whether or not one's bootup toolchain supports zfs this week is another question, one which i sidestep by never having zfs in my boot chain. as a result, i have an annoying mix of mdadm and zfs on these machines.

so it's great tech, but it's not without its annoyances. these annoyances seem furthermore not to be issues of bugs nor design flaws, but operational and philosophical decisions.