For a device that is not expected to be used long-term (e.g. for a few months to evaluate a system), it probably doesn’t matter too much, but if it is something you expect to be using for a long time, I would recommend a brand with a good reputation.
IMO, these brands are Samsung, Crucial and San Disk.
I’m not familiar with WD’s SSD reputation, so I don’t have an opinion about them.
I would avoid PNY products at all cost. Although I haven’t used one of their SSDs, I have used several flash storage and DRAM products from them over the years, and all have failed catastrophically soon after installation (sometimes DOA, and sometimes dead after a few weeks). I don’t think any of their products can be trusted.
Thanks for your suggestions on backing up to an external SSD, or installing Big Sur on an SSD as a test. My question is: can CCC create a bootable 500GB backup of Catalina from my iMac to a 1TB SSD formatted as APFS which already has some files on it? Or would CCC try to use the entire 1TB as a single volume?
Sounds like you need to change the partitioning on the SSD to add one partition in addition to the one already holding files. Disk Utility should let you do that. That new second partition can then be used by CCC as a clone target volume.
@Simon’s approach is best - partition the destination so your backup is separate.
That having been said, one of CCC’s advanced options for a backup task is “Protect root-level items on the destintation”. When checked (it is on by default for new tasks), files and folders in the root of the destination device/folder will not be deleted if they don’t exist on the source.
But it’s still risky to rely on this because root-level items will be overwritten if the source has a matching file or folder. And when you want to clone that volume elsewhere (e.g. when restoring a backup to a computer’s internal storage), you will need to remember to not restore those files/folders.
If there is a reason you must leave those files on the destination volume, may I suggest you do one of the following:
Move them to a folder you know doesn’t exist on the source (e.g. “NotPartOfTheBackup”). This way there’s only one name to potentially conflict and it will be obvious (to you, in the future, when trying to restore the backup) that those files shouldn’t be restored.
Back up to a folder on the destination volume It won’t be bootable, but depending on what you require, that might be OK.
But since your destination volume is APFS already making a new volume in the same container will give you the best of both worlds. The backup volume will be separate from your data, and the pool of free space will be shared between the two volumes.
One final note: If you are backing up Catalina or Big Sur, then the destination device will have at least two volumes - the system volume and the data volume. It will probably also contain a clone of your (hidden) EFI, Recovery and VM volumes.
Alas, no, I’ve always struggled with such things because it’s hard to do enough testing to be comfortable with specific recommendations and then keep that up as the field evolves.
@ace Good point but at the same time there is a wealth of knowledgeable people here that can help balance that concern. Also, perhaps with a caution (like we don’t know? lol) that the opinions expressed are strictly those of the people posting. I have found so many threads here of great value and when I follow through exploring recommendations I figure it is up to me to do due diligence in assessing whatever is recommended. Besides, I have so many wonderful reminders as I go out online that are offered by Amazon, Walmart, fountain pen sites I’ve visited, and I know those are so reliable
I do really appreciate your editorial caution though.
