If the RAID arrays in both location auto Update each other on say a daily basis then place the catalog on an external drive and carry that with you from location to location
The RAID arrays can't sync because there is very poor internet at one of the two locations. I would therefore need to find a way where I can export the catalogue, but then with only the images that I have worked on. Say I have worked on 50 images from different periods, then I would like to only export those including the LR adjustments. Not sure if that is even possible.
I'd use XMP sidecar files. At least for Raw files anyway
When you save metadata (control/command S) it saves all your edits and metadata (bar collections, virtual copies and flagging) into a sidecar XMP files. These files have the same name as the raw, but with the xmp extension. As long as the raw files have the same name on both computers, you can just transfers the xmp files into the folder of the images on the other computer and then use 'Read Metadata from file' (in the right click menu) with all the corresponding photos selected to have the new edits come in.
Edit: The xmp files are tiny, so easy to transfer.
The other option is use an external hardrive with temporary catalogs that you export and import as you go.
Thank you Sean - but how would temporary catalogs work?
I have some 500,000 images on each of my two LaCie 6Bigs. One is located in The Netherlands, one in South Africa. When I upload 2,000 images onto the 6Big in SA and work on many of those images, as well as other images that were already on there, then at some stage I will need to export those images (including the adjustments) and import them again when I'm in NL.
The obvious challenge in that case is: how do I keep track of all the images I have worked on and that need to be added to the other system?
I would like to keep both systems mirrored, without having to physically move them from place to place to clone them. So far, I have not heard a strategy that can do that. Unless I'm mistaken.