[Discuss] Interesting ZFS bug

[Rich Pieri]

https://github.com/openzfs/zfs/issues/11140

Briefly: Flatpak uses fsync extensively. For reasons nobody is entirely
sure about, this causes ZFS to thrash *hard* which I discovered earlier
this week as I finally got around to switching my Calibre install from
Debian's packages (which are woefully out of date). A flatpak
installation that would take at most about 30 seconds on Btrfs or ext4
takes an hour on ZFS.

For me at least, the workaround is to bracket flatpak install/upgrade
commands with disabling and enabling dataset sync:

sudo zfs set sync=disabled zfsroot/zfs/home
flatpak upgrade
sudo zfs set sync=standard zfsroot/zfs/home

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