I have asked LSI and some guys inside VMware if they have any more information on this, but it’s hard to uncover any more information. LSI Support did get back to me, stating:
According to LSI Engineering department, this latency is caused by a bug in the hypervisor. The bug should be fixed in vSphere 5.1 Update 3 and 5.5 Update 2.
It seems this issue will be fixed in an upcoming release of vSphere, so I guess we need to use the work-around until then and hope the fix will actually make the 5.5 Update 2 release. I’m wondering if this issue is LSI-specific, or a more bug more widely affecting other SMI-S providers, too.