How to recover my data
I have fallen victim of this same type of failure on this same type of machine. My 27" imac from late 2012, emc 2546 has the 3TB fusion drive configuration, which is under a recall since last june 2015.
I had no idea that drive could be a potential problem and didn't know there was a recall.
When the drive failed, it did it progressively and silently, and I only noticed at some point that my time machine backups were not completing all the way.
I have an alternate backup external drive that I connect only once in a while for an additional backup besides the main one, so when I started having issues with the backups not finishing, I tried having both backup drives online and alternating between both to attempt to get full backup again and on both backup drives. Since the backups were rather large and would not complete all the way, I excluded some data to reduce the size of the sets, which did work, at first, so I was working my way back to full backup.
I was unlucky and the drive continued failing further and I could not get any good backup, ran out of free space on both external drives, which caused time machine to delete older copies to make room for the new ones that never fully succeeded. When the drive finally failed enough so nothing would work and I could no longer start the machine up from anything, I was left with a non functional mac and an incomplete backup on both backup drives.
That missing data is the most important part for me, as the rest that is backed up is mostly system files and applications, which I can easily replace.
When I found out about the recall, I took my machine to the only local apple store available and they confirmed my machine and its configuration to indeed be covered under the recall.
However my data must be recovered and they could not do it successfully.
All they offered was to simply forget all about my data and get my machine fixed for free under the recall, which is unacceptable, or to ship out my drive to an external 3rd party data recovery company, which is outrageously expensive, and at the same time the recall would no longer apply and I would be invoiced for the imac repair on top of the data recovery from that other company.
A small fortune, which would basically pay for a whole new machine of the same type.
I could not do this, so I just got my machine back.
Now I have that seagate drive 3TB, which is one with the apple specific firmware AP15. The electronics on that drive is faulty and prevents accessing the data and even interferes with starting up the machine from any other drive.
I see many such drives on ebay, but none have the apple specific firmware.
What are the chances of getting a pcb from an other such drive without the apple firmware to actually work properly on this failed apple modified drive?
What interests me above all, is to get the failed drive to work again, so I can get my data back. If then I have to find some other way to get a proper drive back in the machine, so be it. At least I would get my data.
Can anyone point at some useful info about this please?
I'm assuming the issue is with the pcb because this was the cause mentioned by the various technicians at the store that handled the issue. And I also found that when the drive was failing, it was also preventing any other way to startup this machine, from any usb drive, flash or not, and even from the external super drive with an osx install dvd. I would think if the machine is prevented from starting properly from anything other than the failed internal drive, this would also point to something having gone badly wrong with the electronics on the failed drive, perhaps causing issues on the controller.
I have no absolute certainty of course.
And as far as backup is concerned, I did have a proper time machine backup going, one permanently on the machine, plus an other that I connected once in a while and that I also tried connecting at that time while the drive went bad. The failure of the drive happened slowly, silently and progressively. It screwed up a good part of my dual backups, and the most part of what's missing is actually my most precious data. The part that are still on the backups are the least necessary ones, such as the system files, applications, etc... but my needed data is the most part missing. I'm sure a small portion is likely recoverable from the backups, but going after the deleted files, but since the failing backups have rewritten data so many times and cause so many deletions, I don't think enough can be recovered from there.
I am trying to get an other identical drive and attempt a swap of the pcbs. If this works properly and IF the only thing that is truly wrong is on the pcb, then this should solve the problem. However if you're right and something else is wrong with the micro-mechanical stuff inside, obviously this will fail as well and the disk set will need to be the part to be swapped out from the failed drive and put in an other fully functional one.
I know this is supposed to be done in a clean room by skilled techs, but I think the costs are quite high and I can't afford this much.
I am left with a very bad situation and precious data held up in there. I need to find a workable solution.
One thing that I am wondering is if I get an identical drive with the standard seagate firmware instead of the modified apple firmware, is this going to function properly?
In the case that I attempted a swap of the disks inside the drives, not in a clean room, I don't see what this could do for the short term, just the time to do the data recovery, the dust could not really cause any real issues in such a short time...
Here is some reflexion that I'm having about this situation. I believe it's important, and actually vital to properly understand how the fusion drive works and how it's setup, to have any chance of recovering any data.
Everything I've read about the fusion drive until now pointed to the fact that fusion is NOT a caching scheme, where data/files are not duplicated and shadowed on the SDD from the HDD. So the SDD is not used as a separate volume shadowing a part of the HDD.
So here are some very important points that I must be certain about, before proceeding with further tinkering:
1) fusion drive isn't a caching scheme: data isn't duplicated and shadowed.
2) fusion drive is basically a RAID JBOD arrangement, with extra software logic to move files between the SDD and HDD according to how fast we need them to load up, by having the most often used files moved to the SDD
3) the fusion drive resulting volume is an aggregate of the space from both the SDD and the HDD, so the total space is that from the SDD PLUS the HDD
4) the data is spanned across the 2 parts of the fusion drive, not duplicated
5) separating the SDD from the HDD would break the fusion drive and render any data on either useless
Now I'm really not certain that having the HDD removed from the system and the SDD kept in there would be a safe thing to do, because I'm afraid something would happen that would cause a write operation on the SDD, essentially causing the fusion drive to break. I know if nothing special is done with the SDD without its associated HDD, logically nothing should be written to it, but how can we be certain of that?
One other thing to consider is the idea of using a kit to make the failed HDD an external drive via usb or whatever. How would osx behave when seeing its previous fusion drive setup being split across controllers that are different from the previous setup? Having the SDD still in place as before and the HDD moved to an external USB location. Would osx try to consider that a fusion drive again?
If the SDD card is removed, then there is no possibility of confusion.
One other possibility, with the SDD card removed, is to have the failed HDD as an external drive with a hardware write blocker on it, making absolutely certain nothing will be changed on it, as the blocker would intercept any write command to the drive and block them. Then perhaps, if there is a way to make the drive work again, a full duplication could be made from that drive, block by block (by dd ?), to a fully functioning drive of same capacity, which would then allow safe access to the data from the good drive, but then how would that duplicate drive be recognized in the fusion drive if we reassemble it later?
Quite a bit to be addressed before doing the actual data recovery.
All this reflexion should hopefully help other in the same situation, I hope.
I am still expecting the tools that I was missing to work on this imac, but I have received a replacement drive of the same model. That replacement drive is the same model and it dates from roughly the same period, however it's not an apple specific drive with the apple firmware.
Being of the same type, model and rough period, I assume that other drive would be prone to the same kind of failures, so I won't rely on it for the long term. I only plan to use it to recover the data and then I will look at an other replacement drive, hopefully better and I certainly hope not prone to the same issues.
When I get those missing tools, I will then be able to attempt something, and one thing I will try first, before touching anything on the fusion drive, is to try out that replacement drive to bring up the machine to a functional state, where I can run all kinds of tests on the hardware to make sure nothing was wrong beyond the failed drive.
I have not found any reliable info detailing exactly how those faulty drives actually fail. This would be important info to make decisions on the proper methods to use for data recovery, and what to avoid to not have any other problems.
There is also no official source of detailed info about how exactly the fusion drive works. Conflicting info can be found, but overall the consensus about the fusion drive functions is more like what I described earlier on this thread, and that fusion drive is not a shadowing/caching scheme, so the HDD cannot be separated from the SDD and data is not duplicated.
This obviates using the pair of devices together at all times and never at any time try to use them one at a time.
There are issues that I am wondering about though:
1) when using a non apple drive, they are basically identical hardware wise, and although the firmware differs some, electronically it seems to me that they should be the same. So why do we need an extra temperature sensor on the non apple drives? As this would likely be built-in the pcbs and perhaps it's a matter of firmware to relay the sensor's info to the system... Or are there further differences between the apple and non apple drives? would the apple specific drive have extra hardware on the pcbs, along with the different firmware, to read and send the temperature info to the system?
2) if a failed drive has been imaged to a non apple drive, of the same type, but without the apple firmware. Does the fusion drive scheme read anything beyond what's on the drive platters to recognize the HDD to match it with its original SDD? I mean would anything outside of the data recorded on the drive be read to fully identify the drive as being part of the fusion drive to pair it with the SDD? That is drive serial number and such info...
In a case of data recovery that was done by imaging the failed drive to an other of the same type, model and capacity, can the duplicate copy be used as is with the SDD to get back the fusion drive, even though the actual drive is not the original one?
Is this a good question?