Apple Fusion Recovery / Rebuild

[managerharry]

Working on reconstructing an Apple Fusion drive from an iMac. This is a combo device, with a 3tb Seagate drive and a 128GB SSD. System was suffering kernal panics. Apple diagnosed as SSD failure but I have been able to image both drives without any bad sectors. Trying to find more information on how the Fusion drive operates, seems to be similar to RAID0 or JBOD but operates differently. Anyone have details on how this is structured and what software I might be able to use to reconstruct? To ad a rub, the system was configured with a bootcamp partition (visible now on 3tb drive) which I understand is a no-no according to Apple's guidlelines so it must've been setup with a non standard partition structure. I'm trying to access data from the Mac partition which is not mountable.

[managerharry]

possible to rebuild in UFS explorer or similar software?

[Doomer]

Fusion is a span with LVM. SSD drive is first, HDD is second. Learn how Apple CoreStorage operates

[managerharry]

I have read up on Core Storage but there isn't much technical information out there that I have been able to find that details how to non-destructively rebuild a damaged Fusion volume. I have imaged both drives and tried mounting the imaged drives in Disk Utility which does detect the SSD image as a Fusion volume but states that it is missing a disk and prompts to do a destructive rebuild of the volume.

[digisupport]

Have not had any trouble mounting Fusion drives in OSX after recovery, how did you clone ?
What was original problem since you did not find any trouble in cloning ?
Maybe client ruined data before you got your hands on it

[managerharry]

Hmm, it's possible that they screwed the pooch already by writing some data to the 3TB drive. I will get more information from they about what exactly they did with the drive before bringing it in. To confirm though, you are saying that OSX should automatically mount the Fusion volume? Here's where I'm at-- I've imaged the two drives onto replacement disks, the 3tb onto another 3tb and the 128gb solid state onto a standard laptop (non SSD) drive, I then hooked these up via USB to an iMac running Yosemite to see if they would mount, this is where I get the disk missing prompt when disk utility detects the Fusion volume. Is there anything about the process that requires them to be attached internally?

[managerharry]

This system had initially been brought to a not-so-Genius bar where they diagnosed it as a faulty SSD but given that I didn't have any trouble imaging the drive or detect any SMART errors on the SSD (or other drive for that matter) I suspect that perhaps there was a logic board problem or some other software fault that corrupted the volume.

[Dmitri]

This system had initially been brought to a not-so-Genius bar

If I got the situation right, they could have attempted replacing one drive only.

I never tried mounting in OS X, as we usually reassemble such things manually, but if it won't work, I can look into this job remotely.

[managerharry]

No, I'm fairly sure neither of the drives have been replaced, I can see vestiges of partitions on the SSD and the bootcamp partition on 3tb drive is mountable. You say you reassembly manually; any pointers on what the process is? Thanks.

[managerharry]

Anyone else out there have any ideas / suggestions? Any guidance would be appreciated. Thanks!

[data-medics]

Fusion is a span with LVM. SSD drive is first, HDD is second. Learn how Apple CoreStorage operates

I have to disagree with Doomer on this. I've tried rebuilding as a Span of volumes, and pretty much every other way and it doesn't work right. Brand new out of the box it might be that way, but not after usage when it starts moving data back and forth between the HDD and SSD. I think the write buffer portion of the SSD throws everything off if you try to rebuild using standard JBOD techniques.

My solution is to connect the imaged drives to a Mac, boot up using Data Rescue 4 bootable USB and then do the recovery. It'll recognized the fusion array and knows how to properly recover it. Cheers!

[Doomer]

Fusion is a span with LVM. SSD drive is first, HDD is second. Learn how Apple CoreStorage operates

I have to disagree with Doomer on this. I've tried rebuilding as a Span of volumes, and pretty much every other way and it doesn't work right. Brand new out of the box it might be that way, but not after usage when it starts moving data back and forth between the HDD and SSD. I think the write buffer portion of the SSD throws everything off if you try to rebuild using standard JBOD techniques.

I highlighted the important part
Fusion is a span with LVM.

[data-medics]

I guess I was misunderstanding what you were saying as a span of logical volumes. Not a span with a logical volume manager. Anyway, all I know is that my method works. Just did it last week.

[managerharry]

re: data-medics

Interesting. I was planning something similar. Have you tried this with an older iMac that didn't ship with a fusion volume? I tried initially hooking up images drives externally via USB but although it recognized one drive had once been a member of a Fusion volume it was unable to locate the other volume. Do they have to hooked up internally for the system to detect as Fusion volume? I ask since I have an older non Fusion iMac but I was considering installing the imaged drives internally (one in standard slot, and a 2.5" SSD in the DVD slot, and then booting off a USB copy of the OS to try to run recovery software but I'm not sure if that will be a complete waste of time. What the hell, I guess I might as well try it...

[lcoughey]

re: data-medics

Interesting. I was planning something similar. Have you tried this with an older iMac that didn't ship with a fusion volume? I tried initially hooking up images drives externally via USB but although it recognized one drive had once been a member of a Fusion volume it was unable to locate the other volume. Do they have to hooked up internally for the system to detect as Fusion volume? I ask since I have an older non Fusion iMac but I was considering installing the imaged drives internally (one in standard slot, and a 2.5" SSD in the DVD slot, and then booting off a USB copy of the OS to try to run recovery software but I'm not sure if that will be a complete waste of time. What the hell, I guess I might as well try it...

It isn't a matter of the hardware, but the OS version instead. As long as you are running a newer OS version and your images are relatively clean, it should be straight forward.

[managerharry]

I understand that older Macs can be customized with Fusion drives so long as you are running 10.8 or later; my question was more about whether the OS will detect an externally connected Fusion volume (that was originally internal) correctly, perhaps what is throwing off detection of the volume is that the drives are not recognized as say /dev/sda and /dev/sdb as they would be internally but /dev/sdc and /dev/sdd..... hmmm.

[grig85]

Usually just connecting them both to the mac that works. All fusions I've seen are just a simple JBOD setup.

[digisupport]

Usually just connecting them both to the mac that works. All fusions I've seen are just a simple JBOD setup.

+ one

[managerharry]

OK, some further developments. When drives are installed back into iMac system crashes with the attached error screen. If put into target disk mode and hooked up via Tbolt to another Mac running 10.8+ the system it is connected to immediately kernel panics, indeed even booking off Yosemite installer produces swift kernel panic referencing CoreStorage. Ditto single user mode. This means any Mac-based recovery software such as Data Rescue, etc, is out of the question since OSX crashes immediately when system is connect via target disk mode or if booting off USB based OSX. Bootcamp partition is still completely functional & it is possible to boot into Windows but this partition is of course outside of the CoreStorage volume and sees the SSD and 3tb drives as separate volumes. I'm thinking that perhaps the CoreStorage volume was corrupted by partition fiddling in Windows (cust denies this but who knows) or possibly some sort of logic board failure where the system stopped detecting SSD and volume was corrupted. Unless anyone has further ideas I'm thinking on option going forward is raw recovery, scraping partitions for data.

Attachments

[managerharry]

one last thought-- if I remove 3tb drive from iMac, then boot iMac in target disk mode with just SSD, then hookup 3tb drive via USB system does not crash so I could potentially run DataRescue on it that way but DR4.1 at least does not seem to recognize the drives as a Fusion volume. When hooked up this way Disk Utility does recognize as Fusion volume that is missing member.