Edit file init or linuxrc to let your root file system disk adapter appear earlier than all other storage adapters in the same category.

If you don't have another disk handy on your target system, you'll have to edit the installer; you can just extract the archive on your target disk, then update the scripts locally on it.

EDIT: the dataset I'm processing is huge, the raw unsorted dataset doesn't fit on my hard disk. I'm streaming it byte per byte and processing it.