I keep a hard drive containing all my important stuff in an off-site location, in case of complete disaster - including loss of my cloud data or access to it. I've told LR to keep all of my originals on one of my Macs, and as a result I have a .lrlibrary file that's about 350GB.
My question: Is a backup of that file useable in a recovery situation, i.e. could I start from scratch, tell a new copy of Lightroom that these are my photos, and be back in business?
It depends on what disaster you're recovering from. If, for instance, the disaster has struck locally, i.e. your computer or worse, then you don't need to worry about access to that library file. Setup a new computer, install the Creative Cloud app using your Adobe ID credentials, use that to install LRCC, launch it and it will automatically sync with the cloud and present you with the same library that you were using prior to the disaster. If you set the preferences to store a local copy, then all 350gb of files will download again.
If the disaster has struck Adobe and you can't access the cloud, then at least you'll still have you local copy of the originals to use while waiting for Adobe to recover.
Makes sense, thanks. I do still miss having images on my local computer in a format readable without recourse to any Adobe software or storage, as I had with the old (now Classic) LR. When I signed up for CC I didn't realize that the option to keep a copy of everything locally would be in a proprietary format. I guess I can periodically select all my photos and Save them to a local medium. Might take a very long time, but may be a good thing to do once a year or so, just in case of a zombie apocalypse.
We also have a utility that will pull all of your Lightroom CC content from the Creative Cloud to a location of your choosing. It's currently a "use once" solution(all or nothing every time you use it). We're anticipating that at some point down the road customer demand for an incremental solution for local backups will get high enough on the priority list for us to tackle that workflow.