New External Hard Drive for my old iMac

A 2012 iMac has USB 3 ports. On such an old Mac NEVER EVER update it without a backup. Your machine is very obsolete at this point and is almost certainly using an internal hard disk for storage. All HD's fail, the question is when some will last 6 months some will last 10 years but they ALL eventually fail. This makes having a working backup critical as eventually your HD will fail and if it dies without a backup all of your data will be lost.

Buy yourself a 2-4 TB OWC Mercury Elite Pro and connect it to your iMac. Then use Time Machine ( Back up your Mac with Time Machine ) to backup the computer. Once the backup is complete, then you can consider updating Mac OS to the most up-to-date version of Mac OS a 2012 can run. Please remember to test your Time Machine backup after you have done the first backup to verify it is operating properly.

Best of luck.

independentfilmmaker wrote:

Another thing is I haven't updated the MacOS for a while. It's still High Sierra 10.13.6. I want to update to Catalina 10.15, but doing so without back up on an external drive, I have been told, is too risky. Could anyone tell me if, for example, the Toshiba Canvio Partner 1TB HDD or the Seagate Expansion 1TB HDD would work. TIA.

Why not get an external HD, dedicated it to Time Machine and make a backup before you try to upgrade to Catalina. Follow these instructions: How to download and install macOS - Apple Support.

As far as external drives for your Mac I recommend drives from OWC (MacSales.com) as they have proven reliability, excellent customer support and warranties.  Consider one of these depending on your budget and needs: 

OWC Mercury Elite Pro -HDD for Time Machine backups.

OWC Envoy Pro FX Thunderbolt 3 + USB-C Portable NVMe SSD**

OWC Envoy Pro SX Rugged Portable NVMe SSD with Thunderbolt/USB4

OWC Envoy Pro Elektron USB-C portable NVMe SSD

Envoy Pro EX with USB-C or USB 3 

OWC is considered by most here to be the premier 3rd party hardware supplier for Macs.

For your partiucular model contact OWC's customer support and get their recommendation for the SSD model that would best suit your iMac model, work requirements and budget.  They may have additional models other than those I've shown above. Tell them you want it compatible with newer Macs when you upgrade your iMac. They have adaptors for the drives.

That model iMac is considered obsolete by Apple so don't spend a lot of money on hardware that you can't take with you when you upgrade.

Could anyone tell me if, for example, the Toshiba Canvio Partner 1TB HDD or the Seagate Expansion 1TB HDD would work.

They will work, but 1 TB is not much these days. You can buy hard disk drive of twice that capacity for perhaps another $20.

5 TB drives occasionally go for around $100.

SSDs are nice but their speed advantage is totally irrelevant to Time Machine.

You just need a connector that fits the drive you want to use. USB 3 is backward-compatible with USB 2, which your old Western Digital hard disk drive apparently used. You have been using it all the time; it has been operating at USB 2 speeds.

To update macOS, follow these instructions: How to download and install macOS - Apple Support. Scroll down to Catalina 10.15. Use Safari as it states, which will direct you to the App Store.

The Seagate 2 TB Expansion Portable USB 3.0 External Hard Drive is $13 more than their 1 TB version.

4 TB, about $105.

Add another terabyte for $5 more.

You can probably tell what I'd do.