I do understand that, but what are the issues with having the catalog on one drive/location and the image files on another drive? For example in Premiere, files can get moved (and it happen ALL the time) when you get a "Media Off Line" issue when a reference the project (which is a database) refers to a file it can no longer find. You need to reconnect the media by having Premiere locate it where ever it moved to or you put the file back. Not fun, but it works. If that happened in Lightroom, what happens? Do I need to re-connect the catalog to where the files are? Aperture took care of that for you and unless you specifically told it to reference a photograph file where it was instead of bring it into it's library (I know that is not what Lightroom does), it was almost impossible to separate the database from the image files. You coped the entire "package" from one drive to another as essential one file (which contained the database AND picture files), so it prevented anything from ever getting disconnected or separated. Again, I understand LIghtrioom does not do that, but the .DNG files in one folder on one drive and a catalog that points to them on another drive really kinda scares me. For example...
My NAS Drobo has a folder with pictures form, say my last China trip. LOTS of shots, maybe over 1000 .DNG shots. My local hard drive has the Lightroom catalog that points to all those .DNG's....my local hard drive crashes and just say I loose it. Or my computer is destroyed and I need to get a new computer (it's happened, regrettably). I pull up a backup of that catalog, I load it up in Lightroom, will that catalog (database) need to somehow be re-connected to that media? How does it know where they are, especially if the NAS Drobo, say, loads with a difference volume name or something. Doing my best to explain what I mean, so I apologize if its over convoluted.