I'm getting Immich up and running to help backup my pictures littered around different sources (phone / old camera / random local files). The majority of my pics/videos are sitting in iCloud (I pay for the 200GB subscription), then a bunch of old stuff from point-and-shoot Cannon camera (we'll call these "Cannon Pics") is sitting on my Photos share on Unraid.

I am going to leave my Cannon Pics as an "external library" which I believe is read-only and these are all old photos from 1990s-2010). That solves about 10-15k of pictures I have.

I have another 10-15k of pics sitting in iCloud / on my 256GB phone locally. My question is - going forward, should i be using icloudpd and downloading all those into a folder similar to the Cannon Pics which will then be setup as external library? or should i not use icloudpd at all and instead do the mobile app sync of the "recent" folder which as I understand I will need to keep the app open on my phone for some time to process.

Is there any significant downside to going the icloudpd route? I kind of like that my phone is only sync'ing once to icloud then icloudpd does all the background work to get files into immich. But i'm not sure if i'm going to run into issues re- inability to delete (due to icloudpd source folder being mounted as read-only / external library) or duplicates, or deleting pics off my iphone (which syncs to icloud but then icloudpd won't delete the local version in my Photos unraid share causing a bunch of random useless screenshots that i clear out of my Photos app every few weeks).

What do fellow iPhone power users who want a streamlined sync process do with immich?

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Update: Running pro (+) vs. con (-) vs. neutral (~) vs. not sure (?) list:

iCloudPD

• (+) Allows 1:1 mirror duplicate of icloud (via auto_delete=true) which is hyper simple/painless if your only intention is to create a redundant local backup of an existing iCloud backup (which is a 1:1 backup of your local iPhone storage)
• (+) If using icloudPD specifically for redundant backup above (with auto_delete=true), you only need to manage your one main Photos app on iOS to delete random useless pics (screenshots, memes, duplicate/similars and junk) instead of deleting it twice out of iOS Photos and immich app...you manage just "one master library" (your iOS Photos app)
• (+) Operates in background server side, so your iphone is only ever syncing once, seamlessly to icloud instead of running separate immich app for backup (uses less power / heating your phone app / no finnicky backup behavior)
• (-) does not download pictures from shared albums (vs. iOS native backup you can select said album to upload)
• (-) iCloudPD saves into its own folder directory which then can only be set as a read-only external library into immich (does not allow deleting or other other manipulation from immich iOS app)
• (-) iCloudPD requires reauthentication every X days? can use discord webhook notifications to make it easier
• (~) edits from iOS photos app (i.e. auto-enhance, exposure, contrast etc.) don't transfer over when opening same image from iCloudPD share folder
• (?) Is there a method to prevent duplicate files if you initially import your large library via iCloudPD then switch to 100% iOS backup (i.e. backing up the Recent folder)? This is relevant if you want to switch to iOS Native backup after using iCloudPD initially

Immich iOS Native Backup

• (+) Able to precisely and consistently sync specific pics/albums/make deletion of random junk that shouldn't be in the backup from within the iOS app
• (+) if Apple iCloud prices start getting too expensive (or you go past 200GB and don't want to pay $10/month for 2TB) and you want an off-ramp to stop paying for iCloud and transition to immich, iOS method seamlessly works as-is vs. iCloudPD effectively would stop working (you would need to use the CLI import of the local files from iCloudPD share folder then figure out how to not create duplicates i.e. ? bullet above)
• (~) not sure if this is good or bad, but it's effectively a 1 way sync i.e. say you backup 100 photos but then 2 weeks later decide to delete 50 copies within your iOS Photos app (could be useless pics or maybe same picture taken 1-second apart and you only want to retain 1 of them)...your immich backup will still have those 100 duplicate files meaning you have to delete from both sources simultaneously?
• (~) edits from iOS photos app (i.e. auto-enhance, exposure, contrast etc.) are transferred over (and image is reset i.e. can't undo the filter?)
• (-) requires finnicky backup where iphone app needs to be turned on, screen doesn't sleep, uses up iphone resources to upload once to icloud then again to immich