Yes, it is possible, but I would rather store it on the current partition, and transfer the recordings to an archive server with some scripts build in to vicidial.
But if you rather want a partition for it then use yast to create a partition (if you got some free space, don't remember if yast can resize partitions)
if you're on vicibox 4.0.3 then I think you are using OpenSuSE 11.something.
use google if you need a guide on partitioning with yast on your version of OpenSuSE.
and when you are done you could mount the drive directly on /var/spool/asterisk/monitorDONE/ or some of the sub-directories (after you have moved the stuff thats in then right now, so you can move it back in after you have mounted the drive there)
and btw, you wrote "Asterisk 1.4.44 from scratch", I guess you mean "compile from source" you should rather be using the vicidial-patched version of asterisk you can find them here
http://download.vicidial.com/required-apps/
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