[sheepdog] Questions on the virtual disk's cache type

[Liu Yuan]

Hi List,

   I found from the nova/virt/libvirt/driver.py that we set disk cache
mode always as 'none' for crash safety & migration correctness as
commented. But for network volumes such as Sheepdog volume, which
support client side cache, there is definitely use case for users that
want to take full advantage of cache to enjoy best IO performance. So
the question is, is there any customization for cache property? If no,
I'd like to add the cache property capability to glance.

Thanks,
Yuan