Best strategy for using an external SSD when internal drive is too small

For most users what tends to take up large amounts of data are the following libraries:

• Photos
• Music
• Movies

The most simple and effective thing to do is locate and move these libraries to an external drive. Apple explains how to move the Photos library to an External Hard Disk in Move your Photos library to save space on your Mac, the process is the same for Music and Movies libraries.

Gary Wright4 wrote:

Best strategy for using an external SSD when internal drive is too small?

I replicate the folder structure of my user home folder on the external drive and then use the external drive for all data. (Replicate, meaning that I create new folders on the external drive using the same names as the folders in my user home folder.)

• Documents
• Downloads
• Movies
• Music
• Pictures

I then set my various apps to use the folders on the external drive instead of the ones in my home folder. In the case of the Music, TV, Photos, iMovie apps it means moving those libraries to the external drive. In apps like Safari, Photoshop, LR, CaptureOne, Final Cut, etc. it means setting new save locations.

The internal drive is then the home for macOS and applications only, no data. (Full disclosure - there will still be certain data that will continue to be kept in the hidden User Library folder but you can't move that folder. For most people the two largest items kept in the User Library folder are iOS device backups and Mail (email) databases.)

Gary Wright4 wrote:

So no one has said much about possibly moving EVERYTHING to a new external SSD and booting from that as the main (only) drive.

Is that even possible? And if possible, is it a good idea?

It's certainly possible. But I do not believe it's optimum. An external SSD won't yield the full performance of the internal SSD even if it's a Thunderbolt 3 drive.

My suggestion about reconfiguring your iMac is to keep macOS and your apps on the internal SSD and move all possible data to a good external drive (either USB 3.1 Gen 2 (up to 10 Gbps) or Thunderbolt 3 (up to 40 Gbps)). That will allow the system & apps to take advantage of the full speed of the internal SSD.

You are unlikely to notice any difference in data read/write speeds with the external drive unless you are doing multi-track video compositing.

You can move your Photos, Music, Movie Libraries to an external hard drive.

Move your Photos library to save space on your Mac - Apple Support

Change where your music files are stored on Mac - Apple Support

Move your iMovie for Mac library - Apple Support

To protect your libraries, you should back those up using a second drive.

Free up storage space on Mac - Apple Support

Gary Wright4 wrote:

Thanks for the links.

That second link (Change where your music files are stored...) is somewhat confusing. It says, "Important: For best results, don’t change the location of the Music folder or the folders inside it."

It also says, "From now on, new songs and other items you import are stored in the new location. Songs you’ve already imported stay in their current location." That's 31GB I'd like to move to the external drive. Is there no way to move the entire music library to an external drive

You’re welcome.

Music is different than Photos and it can get dicey if you have a mix of music imported from CDs and Apple downloads. Please re-read and follow the directions at > Change where your music files are stored on Mac - Apple Support

The second backup can be your Time Machine. However I also recommend using an additional drive that is keep off line and occasionally updated. I use CarbonCopyClone instead of SuperDuper, but either are great for making incremental backups of your library/libraries.

Gary Wright4 wrote:

So do you feel like it is still necessary to backup you internal SSD, or do you just backup your data drive, only?

I back up data, from wherever it's located. Except for iOS backups, email databases and other data that is hidden in the User Library - all difficult to locate and equally if not more difficult to restore.

Making a backup of the system & apps no longer makes much sense, as it is has become difficult to impossible to do. The system now resides in a sealed "Signed System Volume" and the structure of the boot drive has evolved & changed considerably since the advent of Catalina. Even moreso since Big Sur. Apple advocates using Recovery to restore or reinstall macOS, and that can be done "over top" of existing apps.

Correct, your Time Machine drive ONLY should be used for Time Machine and nothing else. Why, simple....when the drive dies (which they all eventually do) you will have lost your data and it's backup which is pretty foolish. EHD's are relatively inexpensive so simply buy good quality (I'd recommend any drive from www.macsales.com) and use those.

The way Time Machine works, is it backs up everything connected to the computer which means no need for manual drag and drops. If there is something you do NOT want backed up by Time Machine for example your SuperDuper! External Hard Disk then you simply add that and Time Machine will not backup the SuperDuper! drive.

How I have my Mac setup is I have 3 external drives. First like you I have a 4TB OWC Mercury Elite Pro that I use for Time Machine. Next, I have a 2 TB Mercury Elite Pro that I use for SuperDuper!, why a 2 TB you may ask... when I got my iMac I bought a 2TB version so it makes sense for the SuperDuper! External Hard Disk to also be 2TB.

My third External Hard Disk is a RAID 5 OWC Thunderbay enclosure with 48TB of storage. I keep my movies (about 2000 of them), my Photos library and my music library on the beast. I have Time Machine setup to not back this up because in-theory if one of the internal drives on the Thunderbay fails I simply replace it and the new drive will rebuild everything stored on the Thunderbay. I also use SoftRaid to manage everything, SoftRaid comes with the Thunderbay.