How long does it take to consolidate 8TBs in iTunes Library?

I suspect copying 8Tb worth of files might be in the order of days. Instead of one mammoth operation you can select batches of files and use File > Library > Consolidate Files to consolidate just the files in that batch that aren't already in your designated media folder. See Make a split library portable - Apple Community for general background on library organization. I would suggest you start by copying your existing library files into <NewDrive>/iTunes, option-start-iTunes (shift is for Windows) to connect to the new copy of the iTunes Library.itl file, reset the media folder to <NewDrive>/iTunes/iTunes Media, then work slowly from there.

For selecting batches to consolidate you could create a regular playlist called, say, Consolidated, and a smart playlist called Consolidate. Make the rules of the smart playlist Playlist is not Consolidated, and limit to say 1,000 items to start with, selected by Artist. Select all in Consolidate with Cmd+A, consolidate those items, drag the selection to the Consolidated list, a new batch of items will appear. Repeat until done, changing the batch size as appropriate so each batch doesn't tie things up for too long, but you don't have to do too many batches.

tt2

Sounds good. What you might consider is making a small test library with a couple of albums in and then test that you can move that around in the way that you think it should work before committing to action with your full library.

tt2

Consolidating retains checked status, playlist membership, date added, etc. Importing to a fresh library does not. The new Music, TV and Podcasts apps in Catalina are somewhat different from iTunes. If you're going to be using the library with Music rather than iTunes you might prefer to start with the folders Music and Media instead of iTunes and iTunes Media.

tt2

Rats, another lost feature in Music. You can no longer consolidate a selection of files. Using the Automatically Add to Music folder will make copies, which isn't what you want. You may have to go with consolidating the whole library after all. The alternative would be to use a script for the process, but I don't see anything readily available at https://dougscripts.com/. Renaming tracks in their existing folders is easy enough, I've written my own AppleScript for that, and Doug has something that looks quite polished, but it doesn't appear that it can move/copy the tracks to a new volume/path. I've a Windows solution for that, but it isn't a simple port into AppleScript.

tt2

Select a track with an exclamation mark, press Cmd+i to get into, select no when asked to locate the track, then look at the location given on the File tab. Can you find this track on one of your volumes? With both paths to hand I can describe what to do to make the file accessible so that it can be consolidated to the new media folder, along with any others that are in the same set of related folders.

tt2

Ah, got it. A long process then. You should think about a second 20Tb drive and folder cloning software such as Synkron so you can maintain a complete backup of the working version of the library to guard against any drive failure in future.

tt2

I doubt it will be the new drive. You can run disk first aid on all the volumes in turn to be sure. A non-existent volume shouldn't cause a problem. See Re-locate Selected for a script that might allow you to copy/move selected tracks rather than relying on the global consolidate files feature.

tt2

That's a shame. If you can restore tracks to the paths that they used to be on by tweaking volume names and/or moving folders around a little you should be able consolidate those items that have failed to consolidate so far without needing to import, dedupe and repair playlists.

tt2

I'd suggest you don't touch anything that has already copied over.

This entry from Get Info

file:///Volumes/seagate 4tb/Compilations/Walking The Blues/10 Bad Condition.m4a

Tells me that when that file was added to the library the media folder was effectively /seagate 4tb/. You said there were backups. If you have another drive, called bob for example that has a folder called backup inside of which is this Compilations folder, and perhaps other artist folders, then those could be moved to the root folder of bob and bob could be renamed to seagate 4tb. If you now restart Music* it should be able to find the track at /seagate 4tb/Compilations/Walking The Blues/10 Bad Condition.m4a and play it, and if you consolidate the library once more all tracks that weren't previously found but are now visible on their expected paths can be consolidated. Anything that has already been consolidated to the G-Drive will be left alone.

You can repeat the process above as necessary for different batches of music that have been backed up to different drives.

* When you start Music or iTunes it assumes tracks on all paths are available until it has reason to notice otherwise. Once it has noticed that a file cannot be reached because a drive is missing adding the drive, or renaming an existing one, won't change the exclamation mark status. Individual tracks can be repaired by playing them, but consolidate will assume they are missing and ignore them.

tt2