Ceph » rbd

When using rbd export to download images, pagecache is used when reading and writing local files. But there will be some applications, such as qemu, they will use direct io to access files. So there will be inconsistencies at this time. Qemu uses direct io to read files from the hard disk, but the files download by rbd are not completely flush, which will cause serious inconsistency.

If you want to use cgroup to limit the speed of rbd export or rbd import, if not sync io or direct io. Basically does not work.

Combine the above two points, so I want to add the --sync parameter to the rbd export to support this feature. If don't use the -sync parameter, it still read and write in the previous way.