3TB HDD query - Mac Pro 4,1 AHCI

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2013, November 20 - 8:53am

themacmeister

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Joined: 2009 Oct 26

3TB HDD query - Mac Pro 4,1 AHCI

Now, this isn't a standard question, because I know that Mac OS 10.5+ has supported GPT 3TB HDD partitions since the G5 Power Mac days.

I have a "semi-hacked" Mac Pro 4,1 with patched boot MBR for AHCI support, and up-to-date Intel RST drivers for ICH10R chipset SATA2. I tried removing a USB 3TB HDD and using it internal (Bay 2) and it showed up as a weird arrangement of partitions (none working) starting at 867GB or so. I assume that MBR formatted drives of this size need special partitioning software to work correctly (and a 64bit OS).

It is also obvious that Seagate has the smarts in the circuitry that does the SATA->USB connection, to see all 3TB, even though it is not GPT partitioned?!

I want to use a NEW 3TB HDD as an NTFS formatted GPT partition for storage/archive. I know I can convert to a GPT partition using diskpart, but I fear what this may do to my data (1.5TB already).

If anyone has any experience with 3TB drives, and associated pitfalls and problems, please reply.

Many thanks.

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2013, November 20 - 1:30pm

Protocol 7

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Joined: 2010 Aug 7

In the long run I think you're better going to GPT. Disks that size is one of the reasons for it in the first place.

From my own experience, converting to GPT works. I used the linux gpt tool when I was trying to convert my Windows 7 installation from BIOS to UEFI. Ultimately I ran into problems with booting but that was down to Windows and my EFI partition residing on another disk.

The MBR to GPT conversion worked fine. But I did make a whole disk backup first to be sure.

I'd be wary of partitions showing up in the wrong order in Disk Utility. That happened when I was trying to remove unwanted EFI and MSR partitions on one of my disks. The partitions were displaying wrong in Disk Utility. I deleted the right partition, it deleted the wrong one. Lost over 700GB of data. Which was unrecoverable.

2013, November 21 - 10:44pm

(Reply to #2) #3

themacmeister

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Joined: 2009 Oct 26

I have windows and Apple EFI on separate disks too... had no end of issues last time (had to reinstall Mac OS X entirely and Win7 entirely, PLUS all the software!!!).

The entire system works right now (using BootChamp or QuickBoot to get into Windows7) and I have a fully working Boot Camp -> Startup Disk under Win7 where I can select either Win7 or OSX permanently.

I am loathe to make dangerous changes, and since my blank 1TB Seagate internal HDD had it's corrupt firmware meltdown a few nights ago (it can NEVER be used again), I have nowhere to do my backups.

I might just stick where I am and see what happens.

2013, November 21 - 8:57am

themacmeister

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Joined: 2009 Oct 26

A slightly off-topic question.

I ran gptsync (part of rEFIt) and now I have two protective EFI partitions on my single partition OSX boot disk. The boot disk now doesn't show up in Startup Disk prefpane

Is there a non-destructive way to fix this??!!