Bootable RAID 1

[cardinal]

After browsing this forum, it seems there is a consensus that bootable RAID is not possible on hackintosh for 2 reasons: Apple requires GPT partitions to create RAID sets, and BIOS requires MBR partitions in order to boot.

 

I am wondering if hybrid MBR/GPT partitions might be an answer to this. I have not tested this, as I don't have 2 spare disks to try yet. Basically, hybrid partitions means that disk is formatted as GPT, and MBR sectors are "fudged" (contrary to GPT spec) to not show the rest of the disk as one partition of type 0xEE, but to actually point to partitions within the GPT "partition". This is one of the things that makes Boot Camp work. I tried formatting a USB hard drive as GPT in Disk Utility, then using iPartition to mark it as "visible from Windows" (which converts it into a hybrid GPT/MBR), and now darwin fdisk (which is MBR based) sees that I have 2 partitions: one of type 0xEE and the other of type HFS+ which can be made active (and presumably can be booted from on a BIOS computer). Despite the fudging, OS X still sees this as GPT partition and mounts it fine. It also allows me to drag this partition to RAID setup window. I haven't had a chance to try installing OSX and booting from this partition. If that works, the next step would be to create a second drive like that, and make a RAID 1 during installation.

 

Has anyone tried this, or does anyone have 2 spare drives and is willing to give it a shot? After my 3-month old Seagate 320G boot drive died this weekend (it is no longer recognized on POST and is making clicking noise), and after spending almost 6 hours to reinstall everything (thankfully I'm using nightly rsync to back up my home directory to network), I'd much rather run with RAID 1 on my boot drive.

 

EDIT: To make the end result of this partitioning more clear, here is what fdisk sees:

Disk: /dev/rdisk4	   geometry: 7476/255/63 [120103200 sectors]
Offset: 0	   Signature: 0xAA55
	 Starting	   Ending
#: id  cyl  hd sec -  cyl  hd sec [	 start -	   size]
------------------------------------------------------------------------
1: EE	0   0   2 -   25 127  14 [		 1 -	 409639] <Unknown ID>
*2: AF   25 127  15 - 1023 255  63 [	409640 -  119431376] HFS+
3: 00	0   0   0 -	0   0   0 [		 0 -		  0] unused
4: 00	0   0   0 -	0   0   0 [		 0 -		  0] unused

and here is what diskutil sees:

/dev/disk4
  #:				   type name			   size	  identifier
  0:  GUID_partition_scheme					*57.3 GB  disk4
  1:					EFI					200.0 MB  disk4s1
  2:			  Apple_HFS MAXTOR60		   56.9 GB   disk4s2

So, it appears as GPT to GPT-based utilities, and as MBR to MBR based utilities. The question remains, can OS X be installed into this partition, and can it be made into raid and booted from. I'll try installing OS X on this drive, but don't have an extra drive yet to test if it can be RAIDed.

[cardinal]

This is what I did so far, and I would appreciate any suggestions about possible further steps:

 

I formatted two drives as GPT (one internal and one USB) and made a 5G mirror raid on them, from a third drive that has 10.4.8 installed. I then installed JaS 10.4.8 on the mirror. BIOS wouldn't boot from either of the drives with mirrored partitions, not surprisingly since they are GPT. I modified MBR on those partitions to expose GPT partition that was mirrored. Still no boot, and I haven't bothered with startupdisktool yet. Instead, I figured I'd start boot from the drive that currently has 10.4.8, and use rd=diskX option. When doing rd=disk2 (the RAID drive), I get a kernel panic. When using rd=disk1s2 (one of the mirrored partitions), the system boots, but it doesn't see raid properly. There is message during boot that says: AppleRAID - restarting set, AppleRAID - terminating set. Disk utility thinks raid is damaged and shows both raid partitions to be offline. OS X is confused about the fact that it is booted from a broken raid - this partition is mounted as /Volumes/Untitled, while the label in finder is showing "Mirror" (which is what I named the mirror raid).

[blkblt]

Wow, sounds like you've gotten closer than anyone else so far. I'm wondering if something has to be done in the vein of the Natit project where new values are injected into the configuration tree, since I thought RAID relied on some setup from the EFI BIOS.

 

It might be interesting to check a working Mac Pro's ioreg output, since I think those are the only Macs that can boot a RAID drive. This alone is interesting.

 

/blkblt

[cardinal]

Wow, sounds like you've gotten closer than anyone else so far. I'm wondering if something has to be done in the vein of the Natit project where new values are injected into the configuration tree, since I thought RAID relied on some setup from the EFI BIOS.

 

It might be interesting to check a working Mac Pro's ioreg output, since I think those are the only Macs that can boot a RAID drive. This alone is interesting.

 

/blkblt

I'm just fumbling around. I don't have any real understanding of how OS X detects and mounts a RAID startup drive. I learned a lot from these links about Apple RAID and boot process in general:

 

http://developer.apple.com/technotes/tn2006/tn2166.html

http://www.afp548.com/article.php?story=AppleRAID2-in-Depth

http://forum.insanelymac.com/index.php?showtopic=32777

 

If there is one person who could solve this, it is goodtime. He has the chops, but I don't know if he's got time or inclination.

[Korrupted]

It would be nice if people would contribute to this, it could mean that boot camp might work on hackintoshes, making for a lovely bootloader(I can't, as my iHack doesn't support RAID, and I only have one HDD). Also once we get some sort of EFI implementation working(osx86efi) .