The default value hard-coded in QEMU (64KiB) is not always the ideal.
Having a possibility to set the cluster_size by user may in specific
use-cases improve performance for QCOW2 images.
QEMU internally has some limits, the value has to be between 512B and
2048KiB and must by power of two, except when the image has Extended L2
Entries the minimal value has to be 16KiB.
Since qemu-img ensures the value is correct and the limit is not always
the same libvirt will not duplicate any of these checks as the error
message from qemu-img is good enough:
Cluster size must be a power of two between 512 and 2048k
Resolves: https://gitlab.com/libvirt/libvirt/-/issues/154
Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
Reviewed-by: Peter Krempa <pkrempa@redhat.com>
