Attempting to run fstrim on my root partition (which is ext4 on a LVM logical volume, single physical volume—an SSD supporting TRIM) produces an error:
fstrim -v / fstrim: /: the discard operation is not supported
However, running it on a different LV in the same single-PV volume group works just fine. Mount options for both (according to
/proc/mounts) are the same:
issue_discards = 1 is set in
lvm.conf, if that matters.
Why would only one of them support trimming?