Quote:
Originally Posted by dnanian
While you can use images if you must, you can't use read-only images for APFS. In general, as I've said in detail elsewhere, I would discourage the use of images, and as of 10.15.5, it won't be possible to create images of Catalina volumes (we found significant reliability issues).
I strongly encourage you to move away from images and to something more along the lines of iSCSI volumes, if you need to work over a network, or direct-to-drive backups.
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My understanding of the bifurcation of the boot volume into the read-only "System" and Read/Write enabled "data" partitions in the same container is less than perfect, but my guess is that when the SSD in a contemporary Mac fails, it will be time for a new computer because of Apple's love of gluing things into the cases.
That said, I'm wondering if a backup strategy that includes frequent "whole partition" cloning of the "Data" partition, not bothering to copy the read-only system software will be a logical development. I'm assuming that my \Applications and \Library folders are on the "data" partition, and once I get my new (or even repaired, if that's possible) Mac from Apple, it will come to me with an installed System in a read-only partition that I'll need to fluff out with my own "stuff." Is there a way that this could be accomplished by frequent backups of the entire "Data" partition, or even "Smart Copy" backups, not BOTHERING to copy the read-only partition, because internal SSD failure is likely to mandate a new computer purchase anyway?
I ask this because that strategy might be a way to keep rotating platter drives "relevant." My own discovery of just HOW awful rotating platter Catalina Clones are included booting from the SSD and then using Disk Utility to test the clone rotating platter drive. That proceeded acceptably quickly, as does opening data files on the clone while booted from the internal SSD; e.g., a 5 GB 4K movie file on the external opens and plays in a second or two; I can open and edit MS Word files sitting on the external drive with little inconvenience as long as I'm booted from the SSD, whereas when I try to open Word itself when booted from the SSD, I might as well go out for a 2 hour bike ride before trying to work from the file.
Yesterday, a member of the Macsupportcentral email listserv asked what new iMac would be reasonable to purchase today. He was thinking of the base 21" model that comes with a 1 TB 5400 rpm 2.5 inch internal drive. Given what I've learned here, I'm assuming that working with that, or even a 1 TB "Fusion" drive would be a truly painful experience.
I'm also guessing that using external rotating platter drives for Time Machine is still sufficient as well as necessary (Apple limits Time Machine to HFS-formatted volumes), at least until Apple deprecates Time Machine.
To quote Rachel Maddow "Have I said anything stupid or just plain wrong?"
Thanks so much,
Jim Robertson