Error – When you try to enable Fault Tolerance on VMware VM you receive below error.
Device 'Hard Disk 1' uses a controller that is not supported
This error occurs if you are using IDE Disk controller for VM.
IDE disk controllers are not supported by VMware FT and you have to use only SCSI controllers for VMs.
Change VM disk controllers from IDE to SCSI. If you change disk controller from IDE to SCSI, it will make your Guest OS unusable.
So you need to create new VM with scsi disks, Install Guest OS and then enable FT.
If you want to enable FT on Existing VM with IDE disk then you need to do V2V conversion using VMware Convertor.
Follow below KB to convert non-OS IDE Disk to SCSI.