Ceph » rbd

This is something that we should fix. Is it still an issue in current libvirt?

Just checked, problem with blkdeviotune still exists in the 1.0.2.

One thing I noted, which doesn't seem related to RBD is that a Virtual Machine becomes very slow and unresponsive when you hit the I/O limit, much slower then with a 100% utilized disk.

You meant in comparison with physical machine? Qemu is a way slower due to single-threaded self-nature, and seems that it is unsolvable in near future or so.

Andrey Korolyov wrote:

One thing I noted, which doesn't seem related to RBD is that a Virtual Machine becomes very slow and unresponsive when you hit the I/O limit, much slower then with a 100% utilized disk.

You meant in comparison with physical machine? Qemu is a way slower due to single-threaded self-nature, and seems that it is unsolvable in near future or so.

Yes, compared to a physical machine. The VM becomes so slow it's not useable anymore. The throttling works nice though, it's not going over the limits.

With a physical machine stuff still works, but very slow. A VM completely stalls.