For years I have been working with LR on a dell laptop running Windows 10. I bought a new Acer desktop but it only has 512gb in memory... You mean 512gb in disk space, not memory. This is pretty standard these days, and should not be a problem. ... and I have a photo library of 245 gigs If your photo library is on an external HD, this simply is not a problem. This is a solution that works. I thought where I wanted to end up was with my image files stored in the cloud, my backups on a new external HD connected to the Acer desktop and my duplicate imports on the old external HD. Lightroom Classic will not work with photos stored in the cloud. WILL NOT WORK. Perhaps you mean the new software named Lightroom, not Lightroom Classic, which is different. Lightroom (not Lightroom Classic) will work with photos stored in the cloud, but thus far you haven't mentioned what software you are talking about. Now that my latest catalog is happily on the new external HD does that include the backups that were orginally in the LR folder on the old Dell, do I need to move the backups somewhere safer than on the same drive as my catalog and then how do I tell LR classic where those backup files are? It seems you mean Lightroom Classic and not Lightroom. For absolute clarity, please do not refer to Lightroom Classic as "Lightroom". Refer to it as "Lightroom Classic" or LrC. This may (or may not) be the reason why the Adobe agents gave you different answers; one thought your were talking about LrC and other other thought you were talking about Lightroom (not Classic). The location of the catalog file, on the new external HD, does not indicate where the catalog backups are. They can be anywhere. You have to find them and move them to someplace other than this new external HD. Catalog and backups cannot be on the same disk! You don't have to tell LrC where the backups are, it doesn't care; but you should make sure to set the LrC option to store the newly created backups on a differet disk than where the original is located. However you should care where the backps are stored, and always know where the backups are. You should make a new folder on some other disk, at the root level, named Lightroom Catalog Backups so there is never a doubt what is in that folder and since it is at the root folder, it is easy to find. (Some people put catalog backups in some weird folder name buried several folders deep that they will have trouble remembering and DO NOT DO THIS). Also, Lightroom Classic will not work with the catalog in the cloud either.
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