One way of expanding a zpool is to add a new device. For vdevs. it is a zpool add poolname vdev.
On the other, if i have a vdev, but i don’t want to expand the zpool using another vdev, how can i do this? I’ve tried appending additional GBs to the original vdev, but zfs didn’t autoexpand or detect the larger size.
From a purely ZFS perspective, if you had this pool in a mirror/raidz or better configuration, replacing each vdev with a larger, would allow access to a larger zpool (e.g. I used to have a 6x2 TB RAIDZ2 pool, and progressively replaced each 2TB disk with a 4TB disk, allowing ZFS to resilver each time)
However, if this is a single vdev pool, ZFS currently has no way to expand that pool size, other than to do a backup (zfs snapshot+send) and restore into a new pool.
Indeed, auto-expansion is not the default, can you try zpool set autoexpand=on <zpoolname>?
I’ve resized single vdev zpools several times. It works if you can make the underlying disk/part/loopback/whatever device bigger and then ask it to autoexpand.