Hi Steve,
In addition to Rob's real-time solution with the RME RayDat card, I have always just kept a PC with a SCSI controller card and a StorCase receiver frame in it. All my drives are in StorCase trays, so that way I just pop a drive out of the MX-2424 (or it's external Glyph drive chassis) and into the PC for back up at much faster than real-time.
I do this with both a Linux PC and a Windows PC as both still recognize the old Adaptec SCSI controller cards.
Hope this helps!
Kind regards,
Jeffrey Bruton