GPT Protective Partition - out of nowhere

[dandy72]

Hi,

First off, a *huge* thank you for the *fantastic* TestDisk. As I'm writing this, I have it running and recovering/copying individual files that no other tool has been able to identify. I don't really have a specific question about the utility itself, but rather, a general "how could this have happened" type of question. Here's some background details. Sorry for the wall of text, but the Forum Rules section makes it sound like the admin/moderator would rather have all the details up front than having to go through a lot of back-and-forth, which I'm totally in agreement with. So here goes.

I have a pair of 6TB WD Blue hard drives; one a backup of the other. From day one, both have been designated as GPT drives and formatted as a single 6TB NTFS partition on Windows 10. I've never had any problem with either drive. Last year, I bought an 8-bay USB enclosure from Syba (https://www.amazon.ca/dp/B07MD2LNYX?ref ... title&th=1), and moved a bunch of drives to it, which until then had all been sitting in their own enclosure. Everything's been working great for many months. The enclosure's best feature, IMO, is the fact that each bay has its own power button, so you don't have to leave all 8 disks spinning all the time when all you need is to access one of the drives. Most of the time, the entire thing is powered off and I only power drives on individually as I need them.

At some point late last year, I happened to turn on one of those drives (one of the 6TB pair), and Explorer failed to assign it a drive letter, as it would normally do on its own just by powering up the drive. I launched Windows' Disk Manager (diskmgmt.msc), and it identified the drive as one "2048GB partition", marked as "Healthy (GPT Protective Partition)", and the rest as a single "3541GB unallocated" partition. All right-click options are grayed out. Even if they hadn't been, I know better than to try to get Windows to assign a drive letter to either partition while in that state, since they're supposed to be a single 6TB partition.

Not a huge problem, I figured, as time-consuming as it might be, I'll just nuke both partitions into one, reformat it and recover everything from the backup drive. I mean, that's why I take the time to do backups.

I powered on the second drive and...it came up in the same state...(!)

Something had to be bogus. I took one of the drives out and put it in another USB enclosure. Same state, one 2TB "GPT Protective Partition", and the rest unallocated. I hooked up the enclosure to another system, and the same thing again. So, it's not the OS, the drive somehow managed to get itself into that state and this is what every OS is gonna see.

The last time I had used both of those drives was with Windows 10; no problem had ever been reported. I've used those drives in that enclosure for months. I fully realize it's a bit of a stretch, but the one thing that's changed is that the computer's OS drive got wiped and I installed Windows 11 (from scratch, not an upgrade), and it just *so happens* that both drives have shown up in this bogus state since then. I'm not going to blame Windows 11 for that; it's probably just coincidence. Again, if I hook up the same enclosure to another machine still running Windows 10, the drives also come back in the same state.

Now...I mentioned this is an 8-bay enclosure. The other drives in the other 6 bays are absolutely fine, and consist of a mixture of two 5TB drives, two 8TB drives, a 4TB and a 1.5TB.

I had been reading up on what a so-called "GPT Protective Partition" is even supposed to be, and under what circumstances you might see one of those, and even going through articles, I have zero idea HOW two separate drives, sitting independently (but sitting in the same enclosure), could both have started being reported in that state at the same time. I tried a few third-party utilities in an attempt to try to recover the data, but the best one of them could do is to perform a "traditional" file undelete, and completely ignore the folder structure, which is important in my case as there are *many* files with identical names but sitting in different folders in a hierarchy.

I've let the whole thing sit for a few months, not really knowing what to do with this mess, and not quite yet willing to just give up and reformat. The infuriating thing is that I rather religiously backup / resync everything every time there's a significant change...as an aside, what I call a "backup" is really just me manually mirroring the content of one disk to the other, using nothing fancier than robocopy.exe with /MIR. Works for me, and I don't have to rely on some third-party software to read back some proprietary monolithic file that only *it* can read back (which I've always thought was a terrible idea).

Anyway, because both copies of my files happened to be sitting on drives that somehow got in the same unreadable state at the same time...I was sure all the *data* was all still there...but with the partitioning being incorrect, nothing's readily readable.

So as I said, I let it sit for a few months, until I decided today to give it another shot and check with ChatGPT if it could come up with some additional alternatives - and this time around it brought up TestDisk, which until now I had never heard of. The fact that it could "recover partitions" (rather than "recover files") gave me hope it would perhaps take another approach.

And sure enough, I eventually managed to get it to show my original partition, which looked whole and complete and with the proper folder hierarchy. I couldn't find any option to let it write that back ("fix" the partitioning), but it did present options to let me select files/folders and copy them on another drive. So, I took another drive, formatted as a single NTFS partition (> 6TB, so I know I'll have plenty of room), and let it copy files. It's progressing rather slowly - but it *is* progressing, and so far gives no indication of any sort of failure. Given the current speed it's operating at, and the amount of data that was stored on that drive (I actually have an exact figure), it'll take almost 121 hours (5 days) to complete, assuming no slowdown (or speedup), and running 24/7...but if that's what it takes, I'm more than willing to let it run all that time. I mean, it's not like I have much of an alternative.

So again, I don't really have a question specific to TestDisk. But I'm wondering, what could *possibly* have happened so both drives *suddenly* came up in that state, with no warning, at the same time...? What, really, is a "GPT Protective Partition" anyway? I'm looking at the enclosure itself rather suspiciously, but again, the other 6 bays are all occupied by other disks that haven't had that problem.

This is also forcing me to re-evaluate my backup strategy and looking for alternatives. If I can't trust 2 drives in the same enclosure to be a viable option (they're subject to this sort of thing happening, apparently), then what? I suppose I could've kept them both in their original enclosure (I can't imagine I'd ever see this sort of situation if both drives aren't even in the same enclosure), but the entire reason I got this one massive enclosure is to avoid the inconvenience of having to switch cables around when I want to use one drive vs another. Backing up to DVD/Blu-ray media (even at 50GB a pop for a dual-layer Blu-ray) is simply impractical. Tape's too expensive for a home user. Online backups is also impractical given the volume of data. And RAID's not a backup (I've also had the misfortune of having a RAID controller die on me years ago, so I very well understand RAID needs its own separate backup, which is starting to get expensive).

So...again, I have no specific question, but if you're still with me after all this, I'd love to hear some of your thoughts as to what could possibly have happened, given your expertise working with the internal guts of partitions.

Thanks.

[recuperation]

I can't foresee what happened to your disks.
As partition tables only change on your individual actions, they reside on sectors which should only be read during the lifetime of a disk.
That aspect makes finding a reason even more incomprehensible to explain.

If your errors appeared simultaneously they may have been caused when both of your disks where powered on.
If you missed that one disk was already broken, backing this disk up by imaging the source to the target (the other disk) would have cloned that error to a healthy disk.

I never heard the term "GPT Protective Partition", that is logical nonsense, because any kind of "protective partition" appearing in the genuine GPT partition table will never be discovered by a legacy operating system.
The term is "Protective MBR"!

Read here:
https://en.wikipedia.org/wiki/GUID_Partition_Table

If a GPT partition table is being deleted, only the protective MBR remains and will be discovered by a modern operating system and shown as such.

[dandy72]

> I can't foresee what happened to your disks.

Maybe not *foresee*, but I thought maybe it's possible you might have come across this sort of scenario before.

> That aspect makes finding a reason even more incomprehensible to explain.

I figured as much. It *is* incomprehensible to me.

> If your errors appeared simultaneously they may have been caused when both of your disks where powered on.

That's entirely possible.

> If you missed that one disk was already broken, backing this disk up by imaging the source to the target (the other disk) would have cloned that error to a healthy disk.

Agreed, but I don't clone disks; I only mirror changes from one to the other using robocopy.exe with its /MIR switch. Since I didn't even have a drive letter assigned to the partition, robocopy would've simply failed even if I had tried to.

> I never heard the term "GPT Protective Partition", that is logical nonsense

*shrug* It is what it is, I was going to paste a screenshot of Windows's Disk Manager showing *that exact wording*, but it looks like I can only link to an image, not embed one right in the body here. I do have a screenshot, if you have some place where I can upload it without fussing with credentials and the like, I'll be happy to share.