On 04/03/2017 10:07 AM, Michael Hierweck wrote:

Hi all,

virsh checks whether a (live) migration is safe or unsafe. When a migration is considered to be unsafe it is rejected unless the --unsafe option is prodivided.

As a part of those checks virsh considers the cache settings for the underlying storage resources. In this context only cache="none" is considered to be safe.

I wonder why cache="directsync" might be harmfull as it bypasses the host page cache completely.

That's a good question. I too think it isn't harmful. Maybe it's a bug in our code? Michal