Hardware Clock

This page contains the notes from Scott and Colin's session braindumping the expected behaviour of the hardware and system wall clocks.

Players

Hardware Clock:

• A physical clock able to maintain the time while the system is otherwise powered off, either by relying on chemical or mechanical working or though its own discrete power source.

System Wall Clock:

• A software clock maintained by the kernel while the system is powered on.

Network Clock:

• A non-specific accurate clock available over the network.

The hardware clock and network clock are reliable, we can rely on them to maintain an incrementing time while the system is powered off. The system wall clock is unreliable because it cannot.

The system wall clock and network clock are accurate, we can rely on them to maintain the correct time. The hardware clock is inaccurate because it may lose time.