If you want to switch to the paravirtual SCSI adapter in your virtual machine because of performance reasons you can do it like this (this guide assumes you have configured your virtual hard drives as SCSI devices):
The first step is to make sure the paravirtual SCSI driver is included in your initial ramdisk. For this you have to edit /etc/dracut.conf and add the following line:
add_drivers+=" vmw_pvscsi "
and then you have to regenerate your initial ramdisk:
# mv /boot/initramfs-$(uname -r).img /boot/initramfs-$(uname -r).img.bak
# dracut -f
After you have shutdown your virtual machine you have to change the virtual SCSI adapter like this in your .vmx file:
scsi0.virtualDev = "pvscsi"
This has to be done for every adapter which should be converted to a paravirtual adapter.
This was tested on CentoOS 6 and 7.