Thanks for reaching us for the Lightroom CC issue.
The error message which you are getting is due to the following reason.
When you migrate your Lightroom Classic catalog to Lightroom CC, it creates a "cache" of the images which you have in your catalog. The cache is created in the installation drive (which is by default C drive in windows machines.)
Lightroom creates cache of actual images & not of the thumbnails. As per your query your catalog preview & back up data is 12 GB, which means you have a large number of images in Lightroom. You can check the actual size of total number of images you have in lightroom & it will be around 178 GB which is showing by Lightroom CC during migration.
Please check the information which I shared. In case of any issue please share your contact details, we will get back to you at the earliest.
I wish that was true, but I already changed my install of Cc to my secondary drive because for my actual pictures that it’s copying it needed 570GB. The 178GB is just for the previews and whatever picture data, and it’s save location did not change when I changed my install drive.
I believe I am having the same issue. I have a 900GB library on an external drive and a catalogue file with its associated assets that is about 20GB on my internal 256GB SSD.
When I try to import my catalogue into Lightroom CC is tells me I need to have 180GB of storage on my home drive to continue. I have nowhere near that on my Mac's internal drive, so cannot proceed. I tried moving the catalogue and associated files to my external drive and opening it from there, but still no luck. I got the same message saying I had to have enough space on my home drive. So as it stands I cannot migrate my library. There is no way I could free up enough space on the home drive. Very frustrating.
Please provide me your contact details & best time to call, so that we can help you over the call.
I have exactly the same issue. In trying to migrate my large main catalog, the program tells me that I need about 500 GB of free space on my main computer's drive (it's a Mac Pro), and that is far more than I have. I attempted to put everything on an external hard drive where I have ample space but the requirement is for space on the computer itself.
Note that the new library itself, and the designated site for local storage, are both on a large external hard drive.
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In looking into this more, every time I start up a Lightroom CC library that I've placed on an external drive, it creates a new library called Lightroom Library.lrlibrary in the Pictures folder of my MacPro. That's where there's not enough space. It's not apparent how to prevent this default.