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How to use a SoftRAID startup volume with High Sierra

If you're using High Sierra, and booting up from a SoftRAID volume, you'll need to follow the steps given in this forum post, since the macOS High Sierra Installer does not recognize SoftRAID volumes as valid startup volumes.

Alternative to Boot Mirrors?
#1
Preamble: I previously believed in a three disk SoftRAID mirror for my boot volume where the third disk was added, rebuilt, then split off every Friday and stored off-site (as recommended in your eBook years ago). It's saved my bacon several times, but as I've read in the SoftRAID forum Mac mirror boot volumes are on the way out.

In light of the future, consider this:
a single disk boot volume (originally apple disk driver for OS install then SoftRAID) which gets cloned periodically to a second (RAID) disk with two partitions: one (small) partition for the boot clone and a second (big) partition for the TimeMachine backup. This second disk would contain the two primary SoftRAID mirrors(clone&TimeMachine) whose secondaries (on disk #3) would be added, rebuilt, and split off every Friday and stored off-site. (CCC would be used to preserve the recovery partition in the clone.)

Come OS upgrade time the disk driver of the single (main) disk boot volume is changed back to the apple disk driver (SoftRAID5 can do this?) and updated. [The machine would be booted off of the (SoftRAID format) clone on disk#2 for SoftRAID to update the driver on the boot disk to apple format.] Upon restart (the (apple disk driver) boot drive is selected as the boot drive and can be updated by the apple installer.

This approach uses the same two drive bays as the previous "SoftRAID boot mirror" strategy and the occasional drive bay to rebuild the off-site mirror.

Please comment on potential problems or just suggest the simplest backup strategy for single boot volumes [ And feel free to edit the post for clarity.] Thanks for all your efforts.
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#2
Here is the rub;

What you are doing currently is fine, although High Sierra is making it difficult, as each upgrade you need to clone an update to the external, then update (say to 10.13.4), then clone back.

However, the limitation on booting, when it happens completely, will mean even SoftRAID non RAID volumes will become unbootable. The intention is that no non-standard disk/partition map will be bootable in the future.

So a workflow might be:

Boot from Apple formatted internal normally.
Run CCC or SuperDuper daily/regularly to external volume (can be a SoftRAID mirror volume, with a rotated disk as planned)
If the internal fails, then you have to either:
Clone back to internal
Split mirror, Convert to non RAID, then startup from the converted volume.
To save time in the event of a disaster, you should probably keep a clone on an external, Apple formatted USB drive, that can startup your machine if the internal SSD were to fail, or become corrupted.

We have seen several instances of High Sierra updates failing to install on Apple internal disks, leaving the computer non-bootable. The "fix" is rescue boot (command R) and try to repair the volume with Disk Utility First Aid.

We are looking at ways to improve the user experience.

According to Apple's apparent direction, it's possible a MacBook Pro is going to be considered a non serviceable computer, that lasts 3-4 years, then the user should dump it when the SSD fails.

And when that inevitably happens, users should use Time Machine to restore their laptop contents, oer the course of several hours? (Assuming Time Machine can restore to a bootable state, which is never certain.) That solution leaves no room for mission critical projects or use cases.

That seems crazy, if that is Apple's direction. Users want solutions that allow for instantly being able to keep working. That was the idea of SoftRAID. Take the off-site backup disk, buy a new laptop, option boot to your SoftRAID mirror disk, and get working in minutes. That option will no longer be available.

We understand the need for securing the boot process, but bootability via SoftRAID could easily be accommodated if Apple was interested. Its clear they are not.

As a user, all you can do is wait it out and see what solutions become available. We will certainly try to offer "high availability" users some options.
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