I've been a LR user for years going back LR v1. These days I'm using LR Classic but the set up remains essentially unchanged with all my images/catalogue on the local SSD. My image library is approximately 300Gb.
The Macbook Pro I use is old and slow. I'm considering moving to an iPad only solution. But I'm unclear how the storage side works with LR Mobile.
What's stored in the cloud?
What's held locally on the iPAD?
Are there options in how this is configured?
Does it have to be adobe cloud or can I use an alternate?
What's the migration process?
When import from an SD card are the files copied to the cloud, local storage or both?
Is the size of my image library constrained by the space on the IPAD, or the space in the cloud or both?
1. What's stored in the cloud? All images added to Lightroom (either by migration of existing Classic catalog, or import into any of the Lr apps) will be uploaded and stored in the cloud.
2. What's held locally on the iPad (and what options are there)? Ignoring imports directly into the LrMobile app on the iPad (see later), you can download smart previews or originals on a per album basis (or not download anything apart from the automatic basic previews until you need something more substantial). Note that when editing or exporting images from the iPad, a minimum of the smart preview is needed, but if the device is online the original will be downloaded automatically. Those locally stored originals should be deleted automatically by the app over time, but you can always expedite that process using the Clear Cache command.
3. Does it have to be the Adobe cloud? Yes. Understand that it's not just storage space that you are paying for, there's also some very substantial processing that runs on the Adobe servers as well, which needs constant and immediate access to your images.
4. The migration process requires running the Lightroom desktop app, using the catalog migration process, i.e. the app reads your Classic catalog and transfers all images and associated data (edits, metadata) to the cloud. Note that part of the process involves copying all of the local Classic originals to a separate hard drive location (default is the system drive, but that can be changed to a different drive, but best to do that BEFORE starting the migration).
5. Imports from SD card into the iPad app require the originals to be copied into the LrMobile app's designated space on the iPad. From there they are uploaded to the cloud, after which they can be manually removed from the device if needed. Obviously there needs to be sufficient free space on the device to allow all the imports to be copied.
6. Mainly it'll be the cloud space that will be the constraint, though as mentioned there'll also need to be a degree of awareness of the transient space needs on the iPad. Putting that into context, my cloud library is now 21k images which use just over 500GB, but more than half of them are downloaded to my iPhone as Smart Previews (plenty good enough for casual viewing), but the Lr app on the iPhone only uses 15.5GB.