One quirk of ZFS is that deleting a file actually uses a small amount of additional drive space to record the deletion, which causes significant problems if a zpool is ever allowed to fill up 100%.
Fortunately, it’s easy to prevent. As Benedict says:
Don't let your zpool fill up completely by creating a dataset with reservation. # zfs create -o refreservation=<5% of total pool space> <poolname>/reserved You can always shrink the reserve if you need the space, but your pool will always have space left this way. -- Benedict Reuschling [...]
zfs create to reserve the space.
$ su Password: # zpool list -H -o size backup 3.62T # bc 3.62 * 0.05 * 1024 184.32 ^C Broken pipe # zfs create -o refreservation=185G backup/reserved
In case of emergency, use
zfs set to reclaim the space.
# zfs set refreservation=1G backup/reserved