High Sierra - Raid + APFS Insall

I recently upgraded my Mac Mini Server's dual SSDs and found myself needing to re-create the RAID-0 array from scratch. I did this from the command line and formatted the filesystem as APFS. The command

diskutil appleRAID create stripe RAID APFS disk0 disk1

executed without a hitch and I found myself with an apparently fully working dual SSD APFS RAID-0 array. I later used Carbon Copy Cloner 5 to repopulate the drive with my the system's contents, and the operation proceeded without a hitch.

Alas, when push came to shove, I found myself with the cryptic error message

Error loading kernel module cache 0x7

being repeated endlessly on the screen.

There wasn't even a bootable Recovery Partition available. I had to boot into Internet Recovery Mode, which despite its ancient appearance was somewhat helpful: Disk Utility saw the individual drives and their slices, and the RAID array that was spanning them, and reported it as healthy and populated. Unfortunately the Time Machine Recovery client didn't report the drive as being a legitimate target for restoring to.

Apple support was no help at all. The excellent folks at Bombich Software (makers of Carbon Copy Cloner) were much more helpful, despite it being their Thanksgiving holiday.

Meanwhile I literally had to leave the country to resume working at another branch office with a working system because I have an urgent project to complete (I never anticipated rebuilding the machine would take more than a day).

I have now resolved that when I get back to my stricken machine I'll reformat the array as HFS+ and re-image onto that. Quite probably that will work (essentially the same exact situation I was in before I began this, albeit with much bigger SSDs).

Long story short: APFS on RAID looks like it should work, and some report it does, but in my experience it did not and I was unable to figure out why. Beware and be prudent. I will try again if and when Apple announces it officially supports APFS on RAID (which I assume they will do at some ppint, just as they have promised to make it available on hybrid Fusion Drives).

NicholasJurg wrote:

I've read a number of the developer forums but nothing has come back from anyone with a promising result.

You are doing all you can do poking around the Developer Forums. I can not add any more at this time—we will have to let Apple update these concerns in due time.

Space: macOS 10.13 beta | Apple Developer Forums

Hey Nicholas,

I have a Mac mini 2010 with two Samsung 840 EVO 500gb harddisk formated in a RAID running for years.

When I went to SIERRA I had to do the RAID manually with the terminal.

No.. It seems.. If you reformat each drive APFS and them join them in a RAID , then install high Sierra.. "it" works. :-)

Due to time limitations I have not gone this way yet.

Let me know If/when you resolve this chimaera .. hehe.

p

Hi,

I would like to add something to your helpful comment.

Yes indeed the solution you provided will work. Thanks.

Only that potential users must be aware of:

1-Any further OS update will not be applied without formatting and creating the RAID + full installation + restore all over again

2- We are not sure if small security updates, when they are delivered as a combo updates, will be supported and if not where to find a full image of the OS containing those updates to go through the whole process again.

Meanwhile Sierra OSX (not High Sierra so version 10.12.6) is still supported by Apple "as far as I know" and thus, security updates should still be supplied. Version 10.12.6 is very reliable and stable. I do not know of the newer one yet, but I do know that new features are not so spectacular to forcibilly suffer all this hassle. It is on a recent release. APFS is not much quicker on practical live performance. For those for who out of the box encryption is not a must have, APFS will not offer you that much. Surely, there will be a day in which we users, will be forced to switch to a newer version. But that day has not yet come. Let's hope that for that day, Apple will have already changed their silly decision of no supporting installation of new Mac OS on a RAID volume.

Hope this help

All the best!

Here is a thread in another non Mac forum of a guy that did it.

Not very convincing.

https://www.forbes.com/sites/anthonykarcz/2017/09/28/how-to-upgrade-a-raid-syste m-to-macos-high-sierra-youre-not-going-to-like-it/2/#34f353693131

I go with MFRU and wait until all this is resolved or my mac mini 2010 has to be replaced.. hehe.

I do not have such a configuration so obviously cannot test. My guess is that it will install and keep the RAID as is, without converting anything to APFS. That is what happens with either a single HD or a a “Fusion Drive”. HFS+ is still supported. Only single internal SSD are supposed to be converted to. APFS.

You have the backup, so you can decide to try it, or not. Your call.

I am not sure what you meant, but I can tell you that the OS will not even install if that is what you meant. I tried it different times and the installation is aborted always with messages such as: "No drive available for installation" and "you cannot install on a RAID volume". That is not because of trying to convert to APFS at all. It is right at the very beginning of the update process. The installation cannot resume. You are just prompt to restart the machine.

Hi Luis,

You are welcome and I appreciate your help and intention even if did not solve our problem.

I just wish Apple will do the necessary, but I cannot be very positive so far. e.g. I look now at the FileVault that cannot be turned on if the OS is on a RAID volume. They never fixed that. Perhaps it is just technically imposible because of the encryption algorithms they use?? I do not know... But if that was the case and APFS used similar encryption technique, then, we could wait for ages to get a solution.

There is something I can state. The read, write and rewrite speeds on my MacBook Pro 2012 on a RAID Volume with two SSD of 500 GB are: W 970 MB/s, R 610 MB/s and RW near 400 MB/s. I enjoy very much that on the general performance of my PC during my work. With just one SSD it turns to be the half more or less. I do not think that APFS will deliver me these speeds with just one SSD even APFS if actually faster than the current File System. At the end encryption take resources and I only need to encrypt some specific files. No the whole HDD. We encrypt pictures, files and music and then, we upload it to the cloud? That makes no sense to me as far as security concerns.

Moreover I have two SSD of 500 GB that means almost 1 TB at my disposal. I need that HDD size for my professional usage. If I have to buy a 1 TB SSD of the same quality and specs to break the RAID and enjoy High Sierra, then I have to pay almost €400 extra for a PC of 2012.

On the other hand OS built-in security is important to me and I want to be able to get updates without having to reformat, reinstall, covert to APFS, terminal commands for RAID, restore data and apps from Time Machine, etc. So, the move to High Sierra is not worthy for my case unless Apple fixes this problem and I could make use of the RAID volume as it is now. Otherwise I will stick to Sierra 10.12.6 until my PC gets obsolete. It looks to me as rational.

Regards

Ex. mirror APFS in Terminal:

You should see with diskutil list what disks want to include in RAID configuration. If it's boot array you need to build the array from another booted installation an d all your data will be lost from target disks.

diskutil appleRAID create mirror RAID APFS disk3 disk4

I make a 10.13 installation on my Mac mini-server RAID 0 with the OS X High Sierra 10.13 small installer (the 19 MB installer that first appear at the App Store) but I´m not able to get this installer again. If any body has a copy of this one its the solution for this problem.

This is a user-to-user support community, and we cannot speculate on future Apple product deliverables. Apple leadership and product teams do not read, or participate in these communities.

Luis,

What do you mean by "my guess is that it will install and keep the RAID as is"?

Yours

P

I was under the impression that the OS would install on a RAID. I have been shown to be incorrect.

Sorry about that.

Thank you for clarifying. My mistake.

It's OK in SIERRA make RAID manually with the terminal, but in HIGH SIERRA not.

If RAID 0 is relevant to you, it is not recommended to upgrade now.