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Re: Cannot access new Seagate external HD

Cross-posted to 2 groups.

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In article <d5eridF4u7uU1@mid.individual.net>, VanguardLH wrote:
>> I've just added another, a Seagate 'Expansion' 2 TB 3.5" desktop
>> HD (£60).
>> I later found that MBR can 'only support drives under 2 TB'.
> 
> Wrong.  The partition records (4 of them) in the MBR's partition table
> can each handle up to 2 TB *partitions*.

That's sort-of true, in an unuseful sort of way. Any one of those four 
slots could describe a 2TB partition, but you can't use them all.

Each slot contains the start position of the partition as a 32-bit 
number denoting the first sector's LBA, and the size of the partition in 
sectors.

It has been suggested that you could have two 2TB partitions on a 4TB or 
bigger disk by creating on partition at sector 2 with a size of FFFFFFFD 
(so, ending at FFFFFFFE) and another starting at FFFFFFFF with a length 
of FFFFFFFF (so ending at 1FFFFFFFE) -- that would describe the 
partitions accurately, so in a sense you can.

However, the code that manipulates sector numbers in an OS is very 
likely to use 32-bit numbers, so the top bit on any sector number in the 
second partition would be lost, and the result would be that data was 
read from and written to the wrong place. You could probably make it 
work with a specially constructed device driver, but going to GPT is a 
better, safer, and more future-proof way.

> If you bought a 6 TB disk, you could create three 2 TB partitions.

Not with MBR and 512-byte sectors, you couldn't. There's just no way to 
specify that the third partition starts at 200000000 (hex) in a single 
32-bit number.

-- 
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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