Reading Time: 2 minutes VMware vSphere 6.0 has got some issues, like the several related to CBT and data protection, during the first years of its life. Mostly is finally resolved, but you may still have strange issuesespecially during the upgrade procedure (most when you start from a vSphere 5.1 version). I notice, after an upgrade, also a strange behavior with vMotion where live VM migration fails with this error: A general system error occurred: PBM error occurred during PreMigrateCheckCallback: No connection could be made because the target machine actively refused it.