Both of you are missing an important difference between Suspend-to-RAM and
Suspend-to-Disk.
Suspend-to-RAM is a true suspend operation, in that the hardware's state
is maintained _in the hardware_. External buses like USB will retain
suspend power, for instance (assuming the motherboard supports it; some
don't).
Suspend-to-Disk, by contrast, is _not_ a true suspend. It can more
accurately be described as checkpoint-and-turn-off. Hardware state is not
maintained. (Some systems may support a special ACPI state that does
maintain suspend power to external buses during shutdown, I forget what
it's called. And I down't know whether swsusp uses this state.)
So for example, let's say you have a filesystem mounted on a USB flash or
disk drive. With Suspend-to-RAM, there's a very good chance that the
connection and filesystem will still be intact when you resume. With
Suspend-to-Disk, the USB connection will terminate when the computer shuts
down. When you resume, the device will be gone and your filesystem will
be screwed.
Alan Stern
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