How to increase kernel log buffer? Loosing dmesg messages

Continuing the discussion from How to increase kernel log buffer?:

Found previous topic and don’t see if the solution has been implemented. Is there a way to increase the dmesg buffer size? I’m trying to add a hard drive to my NAS box, but it is not listed under /dev/sd* and I can’t see the whole first minute of dmesg (and even less in /var/log/messages) to trace the problem.

Thanks in advance,
Jakub