[alufers]

If you take some basic precautions - disable interrupting the boot process, serial console, etc. then bypassing that requires significant effort. As an attacker you need to know the versions of the software working on the server, know some exploit and then have the experise to use it.

For example I know that the police in my country use off the shelf disk cloning devices and then some basic forensics software for analyzing the disk image. This can be done by an average computer technician, and such a TPM scheme would totally prevent them from extracting data. Of course for bigger cases they can invest some more effort, but they would have to be sure that there is some important data there to justify the cost.