Some questions on 3TB and GPT

blackrain

Golden Member
Feb 15, 2005
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I popped a Seagate GoFlex Home out of the case and hooked it up to my PC. When it first booted, there were 3 volumes on the disk. I was able to delete the first, leaving a 2TB volume and an 700GB volume. I couldn't delete the 700GB volume and after some quick research found this out:
http://knowledge.seagate.com/articles/en_US/FAQ/218619en

But to be quite honest, I don't totally understand it. Does this mean that it is impossible to mount a 3TB drive without GPT? Or are there cases where it can be done without GPT? The Seagate article eludes to the fact that post-2011 BIOS systems don't have this issue. Is GPT native to the new post-2011 BIOS. Or is it something different than GPT in the new post-2011 BIOS? I have an Asus P8Z77-V Pro and i5 just waiting to be used in a replacement build. I imagine that as long I stick to windows 7 or later, I won't have an issue.

Lastly, I ordered this tonight, but its not clear whether the GPT will be a problem or not?
http://www.amazon.com/Plugable-Lay-F...pr_product_top


The other version of this seems to work great with GPT according to some of the reviews:
http://www.amazon.com/Plugable-Docki...ref=pd_cp_pc_1

I just want to make sure that if I am going to load up a 3TB drive that I am going to be able to access it in the future.
 
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dkm777

Senior member
Nov 21, 2010
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I did some research on this topic when I bought my 3TB drives, but that was a while ago and I don't remember all the details. But the things to watch out for are correct BIOS version for your M/B (mine is quite old, but luckily there was a BIOS with GPT support). Next is the version of Windows that you are going to use - Vista with latest SP or later. And finally - NTFS file system. In my case I can't boot from a 3+TB drive, because I have no UEFI, but your board definiely has it so no problems there. And when you are going to make partitions on this disk you have to chech if partitioning software supports UEFI and GPT.
 

VirtualLarry

No Lifer
Aug 25, 2001
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OS needs GPT support for >2TB data volumes. BIOS needs UEFI support to boot off of >2TB volumes.
 

Dufus

Senior member
Sep 20, 2010
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A lot of these USB drives that are more than 2TB come with drives that are 512e but the controller presents them as 4k logical sectors which means they can be used in legacy mode with MBR up to 16TB.

When you take the drive away from the controller and plug direct to SATA then there are going to be problems as logical sector size is now 512B and MBR partition size is only 32-bit so 2TB max.

GPT is just a partitioning scheme so should be able to use it as GPT if configured as a data drive without having to use UEFI. Trying to boot from it though is problematic.

Stick with either 4k sectors through the controller or 512e direct not both, swapping between 4k and 512e after data has been written will cause problems unless you want to start from scratch again.
 
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mv2devnull

Golden Member
Apr 13, 2010
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MBR can address N sectors. When one sector is 512 bytes, the N*512B makes that 2+ TiB. If one sector would be 4kiB, then the product would be bigger as well. In practice, that is a very big if. I've seen only some USB-drives mentioned to present 4kiB sectors (because the USB layer can remap).

In practice, repartition a data disk as GPT.
 

blackrain

Golden Member
Feb 15, 2005
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A lot of these USB drives that are more than 2TB come with drives that are 512e but the controller presents them as 4k logical sectors which means they can be used in legacy mode with MBR up to 16TB.

When you take the drive away from the controller and plug direct to SATA then there are going to be problems as logical sector size is now 512B and MBR partition size is only 32-bit so 2TB max.

GPT is just a partitioning scheme so should be able to use it as GPT if configured as a data drive without having to use UEFI. Trying to boot from it though is problematic.

Stick with either 4k sectors through the controller or 512e direct not both, swapping between 4k and 512e after data has been written will cause problems unless you want to start from scratch again.

Good news is that I don't plan to boot from it. But if I go with my newer mobo and UEFI, would I suddenly be able to boot off that drive (out of curiousity)? Or would I still need to reformat that drive?

As to your second point (which is my biggest concern), I don't know what you mean by stick with either 4k sectors or 512e? I already set up the drive as a GPT and formatted as NTFS. I know that sometimes the windows format application asks how many sectors (or something like that). Where can I check the properties of the drive to determine if I formatted correctly? Also, which would you suggest (4k or 512e)?
 

blackrain

Golden Member
Feb 15, 2005
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MBR can address N sectors. When one sector is 512 bytes, the N*512B makes that 2+ TiB. If one sector would be 4kiB, then the product would be bigger as well. In practice, that is a very big if. I've seen only some USB-drives mentioned to present 4kiB sectors (because the USB layer can remap).

In practice, repartition a data disk as GPT.

That's what I did. Does that automatically set it up as 512 or 4k? Per my other response above, it's not clear to me whether I set this drive up right. I just used the diskpart command in dos, selected the disk, used the "clean" option, and then went into the storage feature in the admin tools. From there, it asked me whether I wanted to make the disk MBR or GPT. I chose GPT. I formatted as NTFS (with whatever default settings there were) but I chose a full format (versus a quick format). Do I need to go back and make sure I selected 512 or 4k and if so, how do I check that?