-- PDL (Permanent Device Loss) Esxi considers device loss permanent. It can be caused by making a LUN inaccessible to a host. This state of PDL is inferred from SCSI sense codes returned for a LUN by an array. ESXi interprets certain codes as a permanent failure.

--APD (All Paths down) Esxi considers connectivity Loss as transient. This can occur if a host can't access the storage array via network. Till 5.x there was no support for handling APD.

Read more: VMware VSphere 6.0 HA---APD and PDL Main Points

• Upto 4 vCPUs per VM (Its a Hard Limit)
• Upto 8 vCPUs per host (User Customizable)
• Upto 4 FT Protected VMs per host (User Configurable)
• Any Disk FT supported like Thin, Thick or EZT
• Hot enable FT supported, means you can turn ON or OFF FT while VM is running.
• Greatly enhanced Host compatible with FT. So now if your hosts are vMotion compatible, most likely they would be FT compatible.
• FT previously was compatible with SRM but now currently isn't compatible with SRM.                              
• FT still is not supported for SDRS, vVols, VCD, VR or stretched clusters (try for stretched Clusters but not supported due to performance)

  Read more: VMware vSphere 6.0 Fault Tolerance - Main Points

Which course is right for me?

When choosing which VMware vSphere® 5.1 training course is right for you, consider your learning objectives, level of familiarity with VMware technologies, the vSphere features you are most interested in and the amount of time you have available for training.

VMware Education Services provides several options that allow you to cost-effectively train a few professionals or a large, geographically diverse audience. Our expert instructors bring real-world experiences and best practices to our classrooms – real or virtual.

Read more: VMware vSphere 5.1 Course Comparison

VMware Certifications

Read more: VMware Certifications Path