It is time, finally, to drop my dumbest ever photo management idea and go back to something sensible.
What did I do?
I have ran my Macs with relatively little builtin storage for modern computers for a long time. This has rarely posed a problem, I have long since abandoned having a local music library, and the majority of data I produce consists of podcast material which I happily offload to my NAS along with anything else of any significant size.
The annoying exception was of course my photos. I have used Apple's Iphoto and then Photos apps as my photo library ever since I got my first Mac. They do all their stuff well enough, but they of course start to really eat into your storage space after a while. Especially as the photos I take only keep growing in file sizes (not to mention the odd video I shoot, why would I not shoot in 4K?).
Falling for the allure of the comparatively infinite disk space on the NAS, I did my Dumb Move: I moved my photo library to a sparse disk image on my NAS.
This seemed to work reasonably at first, but it was clear from the start that Photos really does not want to play that specific game. Even in the best of cases things were always slow. The import process in particular would take forever even for very modest numbers of photos.
Then, the real problems started.
Macos has in my experience never been all that great about maintaining connections to network devices, so Photos in itself may not carry all the blame. And of course the very act of having a sparse disk image on some Linux file system is not something nature intended. In any case, Photos would appear stuck, images would fail to mount, and often the first launch in a while would trigger a very slow library maintenance process before I could do any actual photo management.
Then, I started getting outright error messages, and even slower repair processes only to land in a beachball or new error message. All this of course quickly led me to launch Photos ever less often, meaning everything only took longer and felt even more uncertain each time I got around to it.
Clearly, this can not stand. I have finally come to my senses and bought a drive which can act as a much more locally attached home for the library.
Why not Icloud?
Funny you should ask, I sometimes ask myself too. But even if I did put all my photos in the cloud, I would also want them sucked down to my own complete and local copy somewhere. So while the Icloud photo library would definitely solve some other inconveniences for me, it does not really solve my local library problem.