Can a Lion boot drive be part of an Apple Software RAID?

Question

Can a Lion boot drive be part of an Apple Software RAID?

After many hours of head-banging, I now realize that Lion cannot be installed on a boot drive that is part of an Apple software mirrored RAID (early Mac Pro hardware, Snow Leopard.) Something about a limitation that a RAID drive cannot be repartitioned to allow for the creation of the Recovery partition. Sad, but so be it.

So, I plan to use SuperDouper! to copy my boot drive to a fresh, non-RAID drive, boot from that drive, and then and install Lion there.

Once I have done that, will I be able to add the new Lion boot drive to a new Apple Software RAID mirror set? Or is Lion simply not capable of being booted from a software RAID device?

Thanks in advance!

--david

Posted on May 3, 2012 11:51 AM

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Answer 1

Kappy

Level 10

361,855 points

May 3, 2012 11:54 AM in response to DavidMcCallie

You cannot add it to a RAID without destroying all the data on the drive, but you can create a RAID on which you can install OS X. Note that Lion cannot create a Recovery HD on a RAID array. Practically, you should not use a RAID as a startup volume.

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Answer 2

May 3, 2012 11:57 AM in response to DavidMcCallie

Hi David,

I'm using a striped AppleRAID device as my boot device here. I basically did exactly what you're doing. When I got a new Mac Pro, I used Super Duper! to clone my original Mac's hard drive to a new striped disk set I created.

Can't use Lion Recovery with this, but I have a USB disk I use for that.

See screenshot for my config...

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Answer 3

May 3, 2012 12:08 PM in response to Kappy

Kappy,

Thanks for the quick reply.

Could you clarify why "...you should not use a RAID as a startup disk?" I have been using a mirrored RAID configuration for years as my "main" drive (which I boot off of) and have had no trouble. In fact, the mirror drive saved me once when the other side of the mirror failed.

How would you propose using a mirror to protect your data, but have a non-mirrored boot drive? What parts of the system would go where?

Thanks.

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Answer 4

May 3, 2012 12:11 PM in response to Bernie Case

Hi Bernie,

Thanks for the advice. I am still a little confused. What I was considering was to create a bootable Lion disk (with a recovery partition) and THEN convert the whole thing (including the recovery partition?) to a mirrored AppleRAID. It sounds like that's not possible because of the way the Recovery partition works? Do I have that right?

If so, how did you create a Recovery Partition on a USB disk? Can you point me to those instructions?

Thanks!

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Answer 5

Kappy

Level 10

361,855 points

May 3, 2012 12:17 PM in response to DavidMcCallie

RAIDs are intended to provide fast and large data storage or backup. They are not intended to be used as boot volumes. There are many potential problems that can arise with RAIDs that can cause catastrophic loss of data. Mirrored RAIDs provide no speed benefits, so they are best used to backup a startup volume rather than be used as a startup volume.

On my Mac Pro I have a separate mirrored RAID set up that is used to back up my startup drive. Were one to use a RAID for backup, then this is the configuration I would suggest. It does require three drives: the startup drive and the two drives that make up the array.

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Answer 6

Kappy

Level 10

361,855 points

May 3, 2012 12:19 PM in response to DavidMcCallie

Use the Lion Recovery Disk Assistant 1.0 to create a Recovery HD partition on a USB drive or flash drive. You must already have a Lion system with a valid Recovery HD partition to use the recovery disk assistant.

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Answer 7

Vicent

Level 1

0 points

Oct 17, 2012 1:23 AM in response to DavidMcCallie

Hi David,

I don't know if you are there yet.....

I am in the same problem of you now!. I have a RAID boot partition in Snow Leopard and it is now when i wanto to update to Lion. So, at last, what was your solution for your situation?

Thanks for reading me...

VIcente

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Answer 8

Oct 17, 2012 7:11 PM in response to Vicent

Hi Vicente,

Basically I gave up and used a non-RAID drive as my boot drive. Apparently you can't use RAID as a bootable system drive. I'm not sure, but I think this is because at boot time, the system does not have enough information to understand the RAID disk structures (using a software RAID anyway) and thus cannot read itself to complete the boot. Not sure, but it's a convenient excuse 🙂

Sorry!

--david

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Answer 9

Vicent

Level 1

0 points

Oct 18, 2012 1:02 AM in response to DavidMcCallie

Thanks for answering David....

Ok. Got it. I will design a good recovery plan for the boot drive and I will install it without RAID.

Thank you very much.

Vicente

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Answer 10

Vicent

Level 1

0 points

Oct 19, 2012 4:24 AM in response to DavidMcCallie

Hello Again,

At the end, my process was something like (my memory is horrible):

I take a image of a new installation of Lion in my macbook and I put in a USB external via clone. And I connected this usb-drive to my box in my house.
If you need to expand the volumen (my hd is bigger than the macbook's image) you will not be able to do it. You will need to delete & to create new GPT like this link: http://blog.kyodium.net/2010/11/increase-disk-and-partition-size-in.html. Works perfectly.
Now, the big MUST: use the terminal, diskutil is your friend so after GPT, yes!, you already will be able to do a diskutil resizevolume <volumename> <newsize>. And later a diskutil repairvolumen <volumename> could be useful.
At last, You will need to run a "diskutil appleraid create mirror <drive>" (command is not exact)

It works. Tested. Done in 30 minutes in my case.

So the alternative way to update should be (not tested):

terminal in your snow leopard and sudo -s (it asks currect user pass).
diskutil appleraid delete <raiddrive>, that convert your raid in two individual disk. No more raid but the data persist!!!. You will see two drives in the desktop.
Choose one of them like disk to backup and the other like disk for updating
boot with the disk for updating, it boots normal and install/update Lion. It should install.
Now you use a boot rescue disk and open terminal, yes, there is a terminal there.
sudo -s if you are not root. I don't remember it.
You will need to run a "diskutil appleraid create mirror <drive>" (command is not exact)
reboot and .... it boots. yeah!
Now you will see the other ex-raid-disk (backup disk), now yu can add that other disk to raid via terminal or via disc/drive utility gui of OSX.
may be it is interesting to do: diskutil appleRAID update AutoRebuild 1 raiddrive for a automatic rebuild when you have problems.

Finally: no recovery disk in raid and no FileVault.

Good luck!!!

Vicente

My results

bash-3.2# system_profiler |grep "System Version"

System Version: Mac OS X 10.7.5 (11G63)

bash-3.2#

diskutil appleraid list

AppleRAID sets (2 found)

===============================================================================

Name: DATOS

Unique ID: 0DECFBDC-8375-47D4-B500-3611xxxxxx

Type: Mirror

Status: Online

Size: 999.9 GB (999860862976 Bytes)

Rebuild: automatic

Device Node: disk4

-------------------------------------------------------------------------------

# DevNode UUID Status Size

-------------------------------------------------------------------------------

0 disk1s2 32985705-DECE-46CA-9EE9-D623B6Axxxx Online 999860862976

1 disk0s2 69C848B5-DB83-438E-968B-560E13D9xxxx Online 999860862976

===============================================================================

Name: Macintosh HD

Unique ID: E5B95E3F-F600-4E7F-82F3-3D8D724xxxxx

Type: Mirror

Status: Online

Size: 495.0 GB (494999994368 Bytes)

Rebuild: automatic

Device Node: disk5

-------------------------------------------------------------------------------

# DevNode UUID Status Size

-------------------------------------------------------------------------------

0 disk2s2 71774EF5-5EF9-4557-A2B6-455184Exxxx Online 494999994368

1 disk3s2 09CDD85C-5A58-4ABD-9B7A-A5AB4xxxx Online 494999994368

===============================================================================

bash-3.2#

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Answer 11

calipvp

Level 1

9 points

Mar 2, 2014 10:02 PM in response to Vicent

My Results

bash-3.2$ system_profiler | grep "System Version"

System Version: OS X 10.9.2 (13C64)

bash-3.2$ diskutil appleraid list

AppleRAID sets (1 found)

===============================================================================

Name: Mavericks OS X

Unique ID: C97EDEF2-5E60-4460-B891-70935507422D

Type: Stripe

Status: Online

Size: 999.5 GB (999527546880 Bytes)

Rebuild: manual

Device Node: disk5

-------------------------------------------------------------------------------

# DevNode UUID Status Size

-------------------------------------------------------------------------------

0 disk1s2 9CE5E65F-88F5-47FD-81CB-CF7B4A09FDEC Online 499763773440

1 disk0s2 B7BB7A80-D737-41ED-9117-0B3583864379 Online 499763773440

===============================================================================

bash-3.2$

I know, I know it's Raid 0.... but it's really fast. I can always rebuild my OS drive as all my data resides on other drives.

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