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Groups > comp.sys.ibm.pc.hardware.storage > #6408

Re: Cannot access new Seagate external HD

Cross-posted to 2 groups.

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In article <o2i3vahcmrj3tlsou7lu0cn4e5frk0h9h2@4ax.com>, Terry Pinnell 
wrote:
> And anyway, I later found that MBR can 'only support drives under 2
> TB'.

That's not absolutely correct. If you want the whole story, MBR can 
only support drives that have 2^32 or fewer blocks, and as a block is 
traditionally 512 bytes that means the biggest disk you can have is 
2TB.

.. or, strictly, that you can use a bigger disk but only put 
partitions on the first 2TB of it.

But, if you're using an OS that can work with disks whose blocks are 
bigger than 512 bytes you can use all of a bigger disk and still use 
MBR. [Note that although a lot of modern disks internally use a 4k 
physical sector, they typically then pretend that the sectors are only 
512 bytes, so that's what the OS sees ... and you're back to the 2TB 
limit.]

The 512-byte sector size is so pathologically hard-coded into Windows 
that you can't change it. Linux can support different physical sector 
sizes, so you could probably make MBR work on a large disk, but I 
wouldn't expect all disk management tools to run correctly because that 
512 byte value must be (erroneously) baked into an awful lot of 
sourcecode.

However, the disks you've purchased are not bigger than 2TB, so MBR 
will handle them just fine. It's just that they've been pre-partitioned 
with GPT. You only have to wipe them and repartition.

Note that under the GPT scheme there is a boot record at the start of 
the disk (as usual) and also a backup copy of the partition table at 
the far end of the disk. UEFI firmware may refuse to allow you to use 
the disk as MBR while either of those exists, so you need to wipe both 
of them before repartitioning the disk as MBR.
-- 
Cheers,
 Daniel.
 

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Thread

Cannot access new Seagate external HD Terry Pinnell <me@somewhere.invalid> - 2015-09-10 19:20 +0100
  Re: Cannot access new Seagate external HD Chronos <usenet@chronos.org.uk> - 2015-09-10 19:50 +0100
    Re: Cannot access new Seagate external HD Terry Pinnell <me@somewhere.invalid> - 2015-09-10 20:11 +0100
      Re: Cannot access new Seagate external HD Terry Pinnell <me@somewhere.invalid> - 2015-09-10 20:46 +0100
        Re: Cannot access new Seagate external HD Terry Pinnell <me@somewhere.invalid> - 2015-09-10 21:07 +0100
          Re: Cannot access new Seagate external HD Chronos <usenet@chronos.org.uk> - 2015-09-10 22:10 +0100
          Re: Cannot access new Seagate external HD Mike Tomlinson <mike@jasper.org.uk> - 2015-09-11 00:22 +0100
      Re: Cannot access new Seagate external HD Mike Tomlinson <mike@jasper.org.uk> - 2015-09-11 00:16 +0100
        Re: Cannot access new Seagate external HD Terry Pinnell <me@somewhere.invalid> - 2015-09-11 07:16 +0100
          Re: Cannot access new Seagate external HD Daniel James <daniel@me.invalid> - 2015-09-11 15:17 +0100
          Re: Cannot access new Seagate external HD Shadow <Sh@dow.br> - 2015-09-11 11:30 -0300
          Re: Cannot access new Seagate external HD Mark Perkins <mark@none.invalid> - 2015-09-11 09:35 -0500
            Re: Cannot access new Seagate external HD Mike Tomlinson <mike@jasper.org.uk> - 2015-09-11 21:22 +0100
  Re: Cannot access new Seagate external HD Shadow <Sh@dow.br> - 2015-09-10 16:18 -0300
    Re: Cannot access new Seagate external HD Terry Pinnell <me@somewhere.invalid> - 2015-09-10 21:08 +0100
  Re: Cannot access new Seagate external HD Ed Light <nobody@nobody.there> - 2015-09-10 14:30 -0700
  Re: Cannot access new Seagate external HD micky <NONONOmisc07@bigfoot.com> - 2015-09-10 21:17 -0400
    Re: Cannot access new Seagate external HD Terry Pinnell <me@somewhere.invalid> - 2015-09-11 07:23 +0100
  Re: Cannot access new Seagate external HD VanguardLH <V@nguard.LH> - 2015-09-10 21:11 -0500
    Re: Cannot access new Seagate external HD Daniel James <daniel@me.invalid> - 2015-09-11 15:17 +0100
      Re: Cannot access new Seagate external HD VanguardLH <V@nguard.LH> - 2015-09-12 05:18 -0500
        Re: Cannot access new Seagate external HD Daniel James <daniel@me.invalid> - 2015-09-12 20:46 +0100
          Re: Cannot access new Seagate external HD VanguardLH <V@nguard.LH> - 2015-09-14 04:14 -0500
            Re: Cannot access new Seagate external HD Daniel James <daniel@me.invalid> - 2015-09-14 13:03 +0100
            Re: Cannot access new Seagate external HD Mark Perkins <mark@none.invalid> - 2015-09-14 21:10 -0500
  Re: Cannot access new Seagate external HD Daniel James <daniel@me.invalid> - 2015-09-11 15:17 +0100
    Re: Cannot access new Seagate external HD Terry Pinnell <me@somewhere.invalid> - 2015-09-12 07:05 +0100

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