min_io_size is currently limited to size uint16_t I am using LVM VGs on MD-raid1 for hosting my KVM volumes. On the host, a VG looks like this: Disk /dev/vm/vol202a: 60 GiB, 64424509440 bytes, 125829120 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 131072 bytes / 131072 bytes In order to replicate the block device characteristics in the guest, I am using the following extra parameters: -set device.scsi0-0-0-0.logical_block_size=512 -set device.scsi0-0-0-0.physical_block_size=4096 -set device.scsi0-0-0-0.min_io_size=131072 This doesn't work as qemu complains that min_io_size needs to be of type uint16_t.