Is there any benefit of converting a 2TB non-bootable MBR drive to GPT?

On 1/31/2023 3:34 PM, JJ wrote:
> Is there any benefit of converting a 2TB non-bootable MBR drive to GPT?
>

MSDOS method works from WinXP to Windows 11.

WinXP does not know what GPT is.

At the 2TB capacity point, the choices are otherwise unremarkable.

For larger drives, GPT is definitely the useful one.
(My 6TB backup drives are all GPT.)

The partition choice, does not affect the read/write speed,
given both setups were using the same partition type like NTFS.
It's not a performance issue. On Windows 7, both will be prepared
with 1MB alignment.

Paul

"Paul" <nospam@needed.invalid> wrote in message
news:trchrh$2fgb$1@dont-email.me...
> On 1/31/2023 3:34 PM, JJ wrote:
>> Is there any benefit of converting a 2TB non-bootable MBR drive to GPT?
>>
>
> MSDOS method works from WinXP to Windows 11.
>
> WinXP does not know what GPT is.
>
> At the 2TB capacity point, the choices are otherwise unremarkable.
>
> For larger drives, GPT is definitely the useful one.
> (My 6TB backup drives are all GPT.)
>
> The partition choice, does not affect the read/write speed,
> given both setups were using the same partition type like NTFS.
> It's not a performance issue. On Windows 7, both will be prepared
> with 1MB alignment.

What are the advantages of GPT over MBR when you get to around 6 TB? I
remember when I first bought a 4 TB drive being asked by Windows to choose
between the two, and I wasn't really sure how to choose, beyond the fact
that older versions of Windows don't understand GPT - but the drive was for
Win 7 and I wasn't intending ever to connect it to Win XP. I presume as long
as backward compatibility isn't an issue, GPT is never wrong.

On 2/2/2023 4:10 PM, NY wrote:

> What are the advantages of GPT over MBR when you get to around 6 TB?
> I remember when I first bought a 4 TB drive being asked by Windows to
> choose between the two, and I wasn't really sure how to choose, beyond
> the fact that older versions of Windows don't understand GPT - but the
> drive was for Win 7 and I wasn't intending ever to connect it to Win XP.
> I presume as long as backward compatibility isn't an issue, GPT is never wrong.

If you take a 6TB drive to WinXP, WinXP can only use MSDOS partitioning.

If we do that, you can create any number of partitions, until the first
~2TB are used. Then, there is no way to create partitions on the
remaining 4TB of storage.

There are two drivers, which create "virtual storage". Acronis Capacity Manager
was one of them, and I think there was some Seagate thing. This is how a 6TB
drive appears when a Capacity Manager is used on Windows XP.

+-----+--------------------+
| MBR | 2TB partition | Physical disk 0
+-----+--------------------+

+-----+--------------------+
| MBR | 2TB partition | Virtual disk 1 <=== this drive only appears, if driver loaded!
+-----+--------------------+

+-----+--------------------+
| MBR | 2TB partition | Virtual disk 2 <=== this drive only appears, if driver loaded!
+-----+--------------------+

Imagine the fun if your Macrium CD does not have the driver loaded.

Now, if you want to access that drive on Linux, Linux does not
have a driver for that, so it looks like this.

+-----+--------------------+-----------------------------------------+
| MBR | 2TB partition | 4TB Unallocated space |
+-----+--------------------+-----------------------------------------+

Using loopback mounts, Linux can access all the partitions in the
Capacity Manager diagram, but you need a hand calculator to work
out the offset to find them. I have done that calculation, and mounted
ACM partitions past 2.2TB.

If you use Gnome-disks display program, the Linux diagram of the drive,
looks like the diagram immediately above this paragraph. You can't tell
there are hidden partitions, unless you are Kreskin (the Mentalist).

In any case, the 32-bit addressing in MSDOS partitioning, limits
managed capacity to 2.2TB. This means 2.0TB drives fit fine and
work the way you would expect. It's the much bigger drives, where
the 32-bit addressing limitation is a problem.

**************************************************************************

A 6TB GPT drive looks like this. On any OS that understands GPT.

+-----+--------------------------------------------------------------+
| MBR | 6TB partition |
+-----+--------------------------------------------------------------+

On Linux, a 6TB GPT drive looks like this.

+-----+--------------------------------------------------------------+
| MBR | 6TB partition |
+-----+--------------------------------------------------------------+

On Macrium, with one of the more modern versions of WinPE preparation of a CD, looks like this.

+-----+--------------------------------------------------------------+
| MBR | 6TB partition |
+-----+--------------------------------------------------------------+

Now, isn't that beautiful ? So so uniform. No goofy driver needed! No driver headache.

Yet, if that drive is plugged into WinXP, it looks like this, because
WinXP does not support GPT. (No, it does not look exactly like this,
but this is the logical degree of usefulness of the drive. The drive
is useless to you. Nothing mounts. No storage available.)

+-----+--------------------------------------------------------------+
| MBR | | Boo, and/or Hiss
+-----+--------------------------------------------------------------+

GPT drives contain a protective 0xEE partition of 2.2TB size, and
the existence of this partition is to prevent Windows XP from
accidentally creating partitions on that blank box :-) it's to make
it look like an MSDOS 2.2TB partition of foreign nature is present.
Windows XP cannot mount 0xEE, so it can't do a thing to it. Apple
used a similar trick on their hard drives, having two partition
schemes, and using a protective declaration so an old OS would
not damage a "new" drive format. GPT can use this very same idea.
You can erase the 0xEE from the MBR partition table if you want
(as a bar bet), but sooner or later, something bad is bound to
happen (corruption when accessing the same space, two different ways).

Paul