Comment 0 for bug 1567857

When writing config drive, dd by default uses 512B as the block size. It costs more than 3mins to write the 64M config drive. It's longer than expected: Some health checking(fuel's heat checking) on XenServer may failed due to timeout. So we need improve the performance.

2016-04-07 11:19:19.342 4466 DEBUG nova.virt.xenapi.vmops [req-5e08213e-f8d1-4c59-83ea-3d1cd908a7d5 7456b72259f84038967e9befd72fc388 7fd724d3a16040f6a8f01e43b3c435f8 - - -] [instance: f24c72b3-593c-4f7f-b6ac-f79721f6268a] Updating progress to 40 _update_instance_progress /usr/lib/python2.7/dist-packages/nova/virt/xenapi/vmops.py:962
2016-04-07 11:22:31.961 4466 DEBUG nova.virt.xenapi.vmops [req-5e08213e-f8d1-4c59-83ea-3d1cd908a7d5 7456b72259f84038967e9befd72fc388 7fd724d3a16040f6a8f01e43b3c435f8 - - -] [instance: f24c72b3-593c-4f7f-b6ac-f79721f6268a] Updating progress to 50 _update_instance_progress /usr/lib/python2.7/dist-packages/nova/virt/xenapi/vmops.py:962