iSCSI and NFS, so it looks like my case doesn't depend on storage type.

vdsm.log:
jsonrpc.Executor/2::ERROR::2016-01-31
12:27:52,267::vm::4820::virt.vm::(merge) vmId=`3f560d63-3221-47e4-9786
-bb6cdca8f39c`::Refusing to merge into a shared volume

# vdsClient -s localhost getVolumeInfo 75801b3b-d9ce-4b62-aa36
-6b6519ecc04e 00000002-0002-0002-0002-0000000002db e4fae648-4fea-4f86
-9f24-48894039b8dc e04e1db9-c076-4d2d-8388-311d0d4069e8 | grep voltype
        voltype = SHARED

In my case VDSM even doesn't start live snapshot merging. And if
manually change voltype of my disk on iSCSI from SHARED to LEAF, then
it goes further and hit the bug 1302215. On NFS everything works well
after the hack.

On Sun, 2016-01-31 at 12:56 +0200, Raz Tamir wrote:
> We have a bug opened in the version you mentioned:
> https://bugzilla.redhat.com/show_bug.cgi?id=1302215
> I guess the storage you use is iSCSI?