Remove the support for raw targets #141
Description
When using a raw target, the dump is written directly to a disk/partition without using any file system. Support for raw targets were added with ea179a2 ("adding kexec frontend") in 2006, shortly before makedumpfile support was added. Unfortunately there is no documentation why the raw target was introduced.
My best guess is that at that time RAM was sparse and expensive. So not using a file system allowed to save valuable RAM by reducing the crashkernel memory. In addition, makedumpfile didn't exist back then. So the full /proc/vmcore, which has a quite predictable size, was written to disk. So all in all the trade-off between saving RAM vs. wasting disk space was in favor of using raw targets.
But nowadays the world is different. For one, RAM is quite cheap. So saving a few MB of RAM is less important. In addition makedumpfile reduces the dump size quite a lot (compared to the total memory of the system). But this also makes the dump size less predictable. Meaning you need to add a larger safety to the disk/partition used as target. Otherwise you would risk to have an incomplete dump when the target runs out of space. So today, the trade-off no longer favors the use of 'raw' dump targets.
All in all, I don't think it makes sense to keep the raw dump target. Dropping support for it would allow us to remove some special handling in the code, thus simplifying the code and ultimately reduce the maintenance cost. In addition it would allow the removal of is_raw_dump_target, a wrapper of kdump_get_conf_val, and thus help with #139.