Hello.
Problem Solved.
My case:
i have a pool of many hypervisors with only local storage, no shared SR ( yes it's not recommanded, i stopped doing this and i'm currently migrating everything to pool with Shared storage ).
Yesterday, i removed two hosts ( host 3 & host 4 ) whith local storages SR attached ( LVM ).
In XCP-NG, i "forgot" Host 3 & host 4, the hosts from the pool, but it doesn't forge the associated SR !
But Live migrating a VM from host 1 to host 2 ( of the same pool ) bot with local SR, FAIL because there is no SR plugin attached of Local Storage 4 ( hosts 4 ) neither Local storage 3 ( host 3 ).
So, i also forget theses 2 SRs and now it's ok.
i don't understand why SR not connected to anyone can prevent migration about vm from other to other sr.