Home Forums Peripherals & Multimedia Peripherals Strange problem with hard drive

I have a mid-2012 Macbook Pro. I bought this computer over a newer model specifically because it has an internal DVD drive bay. Why did I do this? So I could take out the DVD drive and replace it with a second hard drive. My laptop has two physical hard drives--a 1 TB SSD and a 500 GB spinning-rust drive. I do this so I can back up critical files (yes, I also back up to an external drive and the cloud as well), since I travel so much and have a lot of files that are extremely valuable.

I recently went to replace the 500 GB spinning-rust drive, which is mounted in the DVD bay, with a 1 TB spinning-rust drive. And, it didn't work.

When I mount the 1 TB drive in the main bay, it works great. When I mount it in an external enclosure, it works great. When I mount it in the DVD bay, it gets constant read/write errors and won't work--Disk Utility won't even successfully format it. It's the same physical size as the 500 GB drive and I know the drive works, so I'm a bit baffled.

Anyone know why a 1 TB drive won't work in a Macbook Pro DVD bay while a 500 GB drive will?

I can only guess the interface cable/"card" is designed differently for the two bays....the main drive bay (and external enclosure) will handle a 1TB target, while the video drive bay interface is falling short of the demand.

Does the System Information SATA tab have any further info to add for you?

It does not. In fact, as near as I can tell, the two interfaces are identical. System Information lists both interfaces as:

Intel 7 Series Chipset
AHCI Version 1.30 Supported

So I believe it's just using the SATA controller built into the Intel platform controller hub, which is a bog-standard part of Intel's support chips for the Intel Core processors. Nothing special (or even non-Apple) about it, and the controller should be able to talk to any SATa device.

so, unless the physical cable holds differences, it's a mystery.....

does it fail while still disassembled, or only once the case is closed?

Years ago corroded contacts in bus connectors, cables, etc. was all too common. Mechanical and chemical contact cleaners used to be a standard item in technician's tool kits.

It still does the same thing when disassembled, so it's not a problem with mechanical pressure or anything like that.



The cable works fine with the 500 GB drive and the DVD drive, so I don't think it's a cable problem.

Unless I missed it, you didn't mention trying the 1 TB SSD in the optical drive bay. That would (presumably) let you rule out the possibility that for whatever reason, the system can't talk to a 1 TB drive in that bay.

So it looks like you have something over 200 years of technogeek quality support going for you here with your issue, so the only thing I might further suggest is to call the "Internet Help Desk"....

I didn't try that, because by the time I reached this point I'd already copied everything onto the SSD and I didn't want to have to go through that again (it took a few hours). I've replaced the 500 GB drive in the optical bay and put the 1 TB spinning-rust drive in an external USB enclosure, but I will admit I'm totally and completely flummoxed. The only thing I can think of is a weird firmware something something that's preventing that SATA port from recognizing a drive over a certain size.

I suspect the key here is "disk utility won't format it". Although you didn't specify the error, I can guess it, "cannot write to last block on device". During the format process, DU will automatically copy block 0 to the last block on the drive. If by chance block 0 gets wiped (back to zeros) Mac OS will automatically restore it from the copy at the end of the drive. I've actually seen this happen, twice, and it still impresses me. (and saves me the time of having to rebuilt it from scratch, a minor pain) It was intended as a nice "it just works" automatic repair feature, but turns out to be a very useful problem detection/early prevention step as well.

Anyway, what this almost always means is that the controller in the computer or the controller in the device cannot access the entire drive. I've had this happen on a couple of flash drives that failed, one flash drive that arrived DOA, and on multiple cases where I was trying to attach a drive that just plain had more sectors than the adapter it was plugged into could access.

One of the most recent times I had this happen is when I was trying to plug in a 2TB drive into a powermac g5. Sure the drive was there, it saw it, it looked good, but DU refused to format it. I think I finally saw the error in console or on the command line. So I got to playing with it and found the last block it could actually access, a neat power of 2 below the 2tb block count on the drive. A little googling and yep, some of that model couldn't access that far.

I've seen internal optical drives hooked up via PATA while the hard drives were SATA, but nowadays they're usually SATA optical drives. But it wouldn't surprise me in the least to find one that had a lower capacity (narrower data bus) than the hard drive's SATA port. So in summary, I'm betting your ODD's SATA port simply can't handle the capacity of the drive. You could get around that by selecting a different drive of the same capacity that used a larger block size. I recently purchased a WD 4TB drive and was caught off-guard by its block size being 4KB instead of 512 bytes. This reduces the block count by a factor of 8, and makes it more backward-compatible. (it would have worked in that G5 despite its large capacity) At this point, the compatibility is limited more by the OS than by the hardware.

I should clarify... just because the data bus isn't wide enough doesn't mean you'll necessarily get errors. The error DU is providing is not necessarily that it's getting an error on the write, it may also be getting an error when it reads the block back to verify it, which it does do. Some drives don't return a write error for OOR, and when you try to read it back will always return zeros for OOR. DU tries to verify the write of the copy of the boot block, and it fails to match, and you get the format failure.

Thanks Virtual1, that's EXACTLY what my intuition was telling me but with a MUCH better explanation....

DU did format the drive, but reported read errors and write errors. When I formatted the drive in an external enclosure it formatted fine (I used the zero disk option to ensure it wasn't a flakey drive), but then when I installed it internally I saw large numbers of read errors after it mounted.

Yeah that really sounds like it can't access the latter part of the drive. There's nothing "wrong" with it, you're just trying to use hardware that's not compatible with that sata port in your computer.

Can you just switch the two internal drives? The HDD SATA port may have a wider bus than the ODD port.

I can't switch ports, because I put a 1 TB solid-state drive on the main port. My goal had been to have two 1 TB hard drives internally in this computer--a SSD on the main port and a backup 1 TB spinning-rust drive on the optical port. That way, I could always carry a full backup with me without needing an external drive.

I've since abandoned that plan. I now have the 1 TB SSD on the main port and a 500-gig spinning-rust drive on the secondary port, which I use to store backups of essential data but not a full system backup. I carry a 2 TB external with me to keep a full system backup (along with the two drives at home that I use to keep rotating backups).

Unless you want to try to find a larger SSD with a larger block size, that's probably your best alternative. (short of going with a 512 SSD in the ODD slot)

And I suspect gathering that information for comparison would be a tedious process, it's not well-advertised.

So it gets stranger.

Intel Macs use a bog-standard Intel chipset with bog-standard Intel SATA hardware, but the Macs use Apple firmware that does some extremely weird stuff with that hardware. The Intel 7 series chipset in my Macbook Pro has no hardware limitations on hard disk size for one SATA port that's any different than the other; that's all down to Apple's firmware.

But wait, there's more!

In addition to the firmware limiting the block size of a device attached to the DVD port, it also limits how EFI booting can take place.

I tried to put a BootCamp partition on the hard drive attached to the DVD port. The hard drive in there boots Mac OS X just fine, but...it can not boot Windows. There's a weirdness in Apple's firmware that causes the Windows bootstrap loader not to be able to boot from any device attached to the DVD port.

I Googled it and apparently, yes, this is a well-known thing. The hardware is capable of booting any operating system from a drive connected to the DVD port, but Apple's firmware prevents it from doing so. The Internets are filled with people who did exactly what I did: bought a Macbook Pro, took out the DVD drive, replaced it with a hard drive, and discovered that it could boot Mac OS X but not Windows.

How absolutely bizarre.

it seems that usually I'm the one to run into weird issues like this. Welcome to my world!