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-   -   Backing up to disk images in Catalina? (https://www.shirt-pocket.com/forums/showthread.php?t=7237)

camner 05-31-2020 10:38 PM

Backing up to disk images in Catalina?
 
I've always used SD's "clone to disk image" feature to keep backups of volumes as part of my backup strategy. (I have a rotating set of 4 drives to which I make a normal backup, and then periodically make a compressed disk image backup for longer term storing of a volume.)

How does this work with Catalina, that has a 2 volume system for each boot drive? Is a disk image backup still possible, and possible to restore from?

dnanian 06-01-2020 07:27 AM

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.

camner 06-03-2020 10:15 AM

Thanks for the reply.

Perhaps you can suggest a better alternative for me...here's my use case:

My laptop has <250GB on it, and because it has no important data on it that isn't elsewhere (because I use Dropbox for data), I only make backups from time to time so I can restore in case of a disaster without rebuilding my system. So, I clone(d) to a disk image which I then stored on a drive with other stuff I want to keep for posterity, and I keep several of those disk images going back about a year.

I suppose one option would be to dedicate a hard drive for these, and then just add volumes as I used to add disk images. If I add a single volume and then choose that as SD's destination of my laptop's boot drive, will SD create the two volumes necessary to make a bootable backup?

dnanian 06-03-2020 12:59 PM

Yes, you can add a volume each time you want another copy, and we'll deal with the details of creating a volume group, etc.

nephdoc 06-04-2020 10:47 AM

Quote:

Originally Posted by dnanian (Post 34715)
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.

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

dnanian 06-04-2020 08:53 PM

That doesn't make sense. We don't copy the system volume if it's not changed (we don't even evaluate it), so there's no need to skip it: you're effectively doing what you're suggesting already.

nephdoc 06-05-2020 10:07 AM

Quote:

Originally Posted by dnanian (Post 34721)
That doesn't make sense. We don't copy the system volume if it's not changed (we don't even evaluate it), so there's no need to skip it: you're effectively doing what you're suggesting already.

It does make sense on another level. If you're me, and well behind the basic curve on how SD works, discovering what it does is in any way akin to what I was suggesting shows that I actually had an idea that turned out to be right!

It's like this: In medical education, there's a time honored educational theater called the CPC (clinical-pathological-correlations). A famous professor from another medical school, visiting and showing off his diagnostic skills, is presented the story of a single patient. Typically, that story ends with a critical diagnostic test that establishes the cause of the patient's problems, or sometimes with the patient's demise with the cause of his or her problems still undiscovered. The visiting honcho is not given the result of that test, or even what the test was (unless the patient died, and then it's obvious that it will be an autopsy.

Then, the hotshot from Boston, or Cleveland, or San Francisco, or Vienna, or wherever, takes over and displays his perceptual magic, after which the pathologist appears from the basement to tell everybody what was REALLY wrong with the patient.

Typically, after the wizard from St. Elsewhere's skills are affirmed or shown to be lacking, the next slide in the PowerPoint (or, in Apple's resurgence, Keynote) presentation is a summary of all the Med Students' diagnoses.

The story goes that in one such bit of mental acuity theater, ALL of the medical students but one had the wrong diagnosis, as did the visiting maven, EXCEPT for a guy (we'll call him Jim) who was clearly known to be the class dufus.

The patient's original complaint had been something wrong in his belly, which turned out to be an enlarged spleen. Now, there are literally dozens, if not hundreds of causes of "splenomegaly," and the greatest diagnosticians are legendary for ferreting out other clues that lead to inference of the cause of an individual patient's diagnosis when that's the presenting abnormality.

The out-of-town professor in this case didn't know that his famous talents had been bested by the local class clown, so he was a bit surprised by the giggling and murmuring when Jim's name appeared on the giant monitor as the only person to get the diagnosis right. The correct diagnosis had been "primary malignant sarcoma of the spleen," and Jim's diagnostic proposal had been "spleen cancer." Technically, sarcoma and carcinoma are a bit different, but still, Jim had been fundamentally right. So, the visiting prof asked him to stand and run through his own thought processes that had led him to the correct diagnosis.

Jim replied, with no hint of embarrassment, "so, what ELSE makes your spleen get big?"

So now, Jim #2 asks your indulgence for 2 more questions:
  1. Do you know when the Catalina-compatible 10.15.5 SD will be ready?
  2. Do you have any inkling whether a typical user forced to work from his/her clone for a while would be able to tell the difference between one based on a Sandisk portable external with USBc interface vs. OWC's NVMe "blade" SSD connected via TB3?

By the way, my own time in medical academia predated Mac OR PC, but by the time I was attending giant hotel annual meetings of professional societies as a practicing doc, EVERYONE had given up on the "Diazo-Blue" acetate transparencies that would melt from the heat generated by the thousand-watt incandescent bulbs that projected their content on enormous screens in the hotel ballrooms if the speaker lingered too long on one slide.

EVERYONE by then (late 1980s-early 90s) used their HP or Compaq Windows laptops, and typically when one presentation followed another, either the presenter would bring his laptop to the front and fumble with connecting it to the projector, or with rebooting the hotel's laptop, or stuffing his presentation floppies into the computer, or getting his presentation to fill the screen rather than being overlain by his grocery list in a window, or the IT guy would fumble with the projector refresh rate, or they wouldn't have the proper interface cable.

Inevitably, as the audience began to murmur like an angered British House of Commons, someone would call out from the audience "GET A MAC!!!!!!!"

Thank you so much for your unbelievable patience and generosity with your time!

dnanian 06-05-2020 10:21 AM

Yeah, I should rephrase my response as "it's unnecessary, since we already do that". :)

1. We're working on it. Dates are hard.
2. Probably not. Probably.


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