can't convert 4 TB GPT external USB 3 HD to MBR?

I just picked up a 4 TB WD external USB 3 HD for back up purposes. I
use Win 7, Ubuntu, and XP. I can easily see and manipulate the drive
contents in '7 and Ubuntu, but not XP. I know this has to do with the
GPT protective partition. In the past, I just used some software to
convert to MBR, but the same software doesn't seem to want to do it this
time. I'm unclear as to the reason (MBR restrictions?), but I believe
it's saying that I need to partition this 4 TB disc into partitions that
are no more than 2 TB in size--- would this happen to be correct?

I would like the drive to be seen in XP as well as my other two OS.
Trouble is, I already have more than 2 TB of data stored on it before I
realized that I couldn't convert it. Should I leave it as it is and
just forget using it in XP too, or is there a workaround?

Thank,
Eric

Eric S on 2016/12/07 wrote:

I just picked up a 4 TB WD external USB 3 HD for back up purposes. I
use Win 7, Ubuntu, and XP. I can easily see and manipulate the drive
contents in '7 and Ubuntu, but not XP. I know this has to do with the
GPT protective partition. In the past, I just used some software to
convert to MBR, but the same software doesn't seem to want to do it this
time. I'm unclear as to the reason (MBR restrictions?), but I believe
it's saying that I need to partition this 4 TB disc into partitions that
are no more than 2 TB in size--- would this happen to be correct?

I would like the drive to be seen in XP as well as my other two OS.
Trouble is, I already have more than 2 TB of data stored on it before I
realized that I couldn't convert it. Should I leave it as it is and
just forget using it in XP too, or is there a workaround?

The MBR (master boot record) contains the partition table. There are 4
partition records in the partition table. Each partition record can
address up to 2^32 sectors. Each sector is, by default, 512 bytes. So:

2^32 sectors * 512 bytes/sectors = 2,199,023,255,552 = 2 TB.

There's your limit. MBR's partition records cannot support partitions
greater than 2 TB in size.

https://en.wikipedia.org/wiki/Master_boot_record
"MBR partition entries and the MBR boot code used in commercial
operating systems, however, are limited to 32 bits.[2] Therefore, the
maximum disk size supported on disks using 512-byte sectors (whether
real or emulated) by the MBR partitioning scheme (without using
non-standard methods) is limited to 2 TiB."

Eric S wrote:
I just picked up a 4 TB WD external USB 3 HD for back up purposes. I
use Win 7, Ubuntu, and XP. I can easily see and manipulate the drive
contents in '7 and Ubuntu, but not XP. I know this has to do with the
GPT protective partition. In the past, I just used some software to
convert to MBR, but the same software doesn't seem to want to do it this
time. I'm unclear as to the reason (MBR restrictions?), but I believe
it's saying that I need to partition this 4 TB disc into partitions that
are no more than 2 TB in size--- would this happen to be correct?

I would like the drive to be seen in XP as well as my other two OS.
Trouble is, I already have more than 2 TB of data stored on it before I
realized that I couldn't convert it. Should I leave it as it is and
just forget using it in XP too, or is there a workaround?

Thank,
Eric

Acronis Capacity Manager (part of one of the disk tools
that both Seagate and WDC offer), makes a physical 2TB
drive and a virtual drive with the rest of the space.

That works with a SATA-connected MBR disk.

However, it doesn't work with USB connected media.
I moved my ACM-prepared disk to a USB enclosure,
and the scheme promptly stopped working. I could
not access the top part of the disk drive.

There is at least one other scheme besides Acronis,
so don't give up.

http://www.ghacks.net/2010/11/04/how...on-windows-xp/

"Paragon however came up with a solution. They basically
create a specially signed driver to make Windows XP
compatible with the GPT partitioning scheme."

https://www.paragon-software.com/tec...ts/gpt-loader/

Paragon GPT Loader $19.95

Now, I haven't tested it, And you know damn well,
it'll have rough edges and limitations. At least they
stated what the limits are.

"Only internally connected single 2.2TB+ drives are supported,
not external storages, or those combined into RAID
(Redundant Array of Independent Disks)"

So that *still* doesn't solve the big USB drive issue on WinXP
in a completely seamless way.

If the enclosure was "USB3/ESATA" and had two different
cabling schemes, you could put an ESATA interface card
in the WinXP machine. But that adds a lot of expense,
to make the external drive into what is effectively
a "SATA Tray drive".

Keep looking.

Paul

On 12/08/2016 02:49 AM, Paul wrote:
Eric S wrote:
I just picked up a 4 TB WD external USB 3 HD for back up purposes. I
use Win 7, Ubuntu, and XP. I can easily see and manipulate the drive
contents in '7 and Ubuntu, but not XP. I know this has to do with the
GPT protective partition. In the past, I just used some software to
convert to MBR, but the same software doesn't seem to want to do it
this time. I'm unclear as to the reason (MBR restrictions?), but I
believe it's saying that I need to partition this 4 TB disc into
partitions that are no more than 2 TB in size--- would this happen to
be correct?

I would like the drive to be seen in XP as well as my other two OS.
Trouble is, I already have more than 2 TB of data stored on it before
I realized that I couldn't convert it. Should I leave it as it is and
just forget using it in XP too, or is there a workaround?

Thank,
Eric

Acronis Capacity Manager (part of one of the disk tools
that both Seagate and WDC offer), makes a physical 2TB
drive and a virtual drive with the rest of the space.

That works with a SATA-connected MBR disk.

However, it doesn't work with USB connected media.
I moved my ACM-prepared disk to a USB enclosure,
and the scheme promptly stopped working. I could
not access the top part of the disk drive.

There is at least one other scheme besides Acronis,
so don't give up.

http://www.ghacks.net/2010/11/04/how...on-windows-xp/

"Paragon however came up with a solution. They basically
create a specially signed driver to make Windows XP
compatible with the GPT partitioning scheme."

https://www.paragon-software.com/tec...ts/gpt-loader/

Paragon GPT Loader $19.95

Now, I haven't tested it, And you know damn well,
it'll have rough edges and limitations. At least they
stated what the limits are.

"Only internally connected single 2.2TB+ drives are supported,
not external storages, or those combined into RAID
(Redundant Array of Independent Disks)"

So that *still* doesn't solve the big USB drive issue on WinXP
in a completely seamless way.

If the enclosure was "USB3/ESATA" and had two different
cabling schemes, you could put an ESATA interface card
in the WinXP machine. But that adds a lot of expense,
to make the external drive into what is effectively
a "SATA Tray drive".

Keep looking.

Paul

Thanks, I'll keep looking. In the meantime, I'll just have to use my
other less than 2 TB drives with it. At least I can still back up the
XP machine to the 4 TB drive using True Image, which was one of my main
purposes for having the 4 TB drive.

For a while, I've been thinking of upgrading my XP machine to Win 7, but
I have so many configurations set up that I know I couldn't remember
them all in '7. I guess I could always try the Win 7 files migrator/
configuration transfer (I forget exactly what it's called), but for
something like the Virtualbox VM's, I have them set up in such a way
that I don't know if they'd ever be configured properly in '7.

Eric S wrote:
On 12/08/2016 02:49 AM, Paul wrote:
Eric S wrote:
I just picked up a 4 TB WD external USB 3 HD for back up purposes. I
use Win 7, Ubuntu, and XP. I can easily see and manipulate the drive
contents in '7 and Ubuntu, but not XP. I know this has to do with the
GPT protective partition. In the past, I just used some software to
convert to MBR, but the same software doesn't seem to want to do it
this time. I'm unclear as to the reason (MBR restrictions?), but I
believe it's saying that I need to partition this 4 TB disc into
partitions that are no more than 2 TB in size--- would this happen to
be correct?

I would like the drive to be seen in XP as well as my other two OS.
Trouble is, I already have more than 2 TB of data stored on it before
I realized that I couldn't convert it. Should I leave it as it is and
just forget using it in XP too, or is there a workaround?

Thank,
Eric

Acronis Capacity Manager (part of one of the disk tools
that both Seagate and WDC offer), makes a physical 2TB
drive and a virtual drive with the rest of the space.

That works with a SATA-connected MBR disk.

However, it doesn't work with USB connected media.
I moved my ACM-prepared disk to a USB enclosure,
and the scheme promptly stopped working. I could
not access the top part of the disk drive.

There is at least one other scheme besides Acronis,
so don't give up.

http://www.ghacks.net/2010/11/04/how...on-windows-xp/


"Paragon however came up with a solution. They basically
create a specially signed driver to make Windows XP
compatible with the GPT partitioning scheme."

https://www.paragon-software.com/tec...ts/gpt-loader/

Paragon GPT Loader $19.95

Now, I haven't tested it, And you know damn well,
it'll have rough edges and limitations. At least they
stated what the limits are.

"Only internally connected single 2.2TB+ drives are supported,
not external storages, or those combined into RAID
(Redundant Array of Independent Disks)"

So that *still* doesn't solve the big USB drive issue on WinXP
in a completely seamless way.

If the enclosure was "USB3/ESATA" and had two different
cabling schemes, you could put an ESATA interface card
in the WinXP machine. But that adds a lot of expense,
to make the external drive into what is effectively
a "SATA Tray drive".

Keep looking.

Paul

Thanks, I'll keep looking. In the meantime, I'll just have to use my
other less than 2 TB drives with it. At least I can still back up the
XP machine to the 4 TB drive using True Image, which was one of my main
purposes for having the 4 TB drive.

For a while, I've been thinking of upgrading my XP machine to Win 7, but
I have so many configurations set up that I know I couldn't remember
them all in '7. I guess I could always try the Win 7 files migrator/
configuration transfer (I forget exactly what it's called), but for
something like the Virtualbox VM's, I have them set up in such a way
that I don't know if they'd ever be configured properly in '7.

You could use file sharing, connect the external drive to a
GPT capable system, and do the backup to a network
share.

Machine #1 Machine #2
---------- ----------

WinXP
|
Macrium -------- Win7_Machine --- Ext_4TB_drive (GPT)
File (shared disk, fixed letter)
Sharing

But that's not going to make the bare metal restore
later all that easy. You have to make sure on Macrium, that
you have the drivers for network included on the disc made
especially for the WinXP system. Each machine should
have its own backup CD, to aid in having "all drivers"
when the restore starts.

To test that, you can even do the backup operation
from the CD, to ensure everything is functional.

As part of the verification effort, you can run
Macrium on the Win7 machine, after your first backup
run is complete, and do a "Verify" command on the MRIMG
file on the disk drive. This proves that the network
did not corrupt the transfer. This is important, if
a year later you were expecting a perfectly good file
to be on the External drive. You can also do the operation
from the WinXP machine if you want. The verification
will drag the file across the network again while the
checksum is computed.

Paul

VanguardLH wrote:


The MBR (master boot record) contains the partition table. There are 4
partition records in the partition table. Each partition record can
address up to 2^32 sectors. Each sector is, by default, 512 bytes. So:

2^32 sectors * 512 bytes/sectors = 2,199,023,255,552 = 2 TB.

There's your limit. MBR's partition records cannot support partitions
greater than 2 TB in size.

Not quite. Those entries contain the beginning and ending locations of
each partition. So the MBR format can't handle a *disk* larger than
2TB.

https://en.wikipedia.org/wiki/Master_boot_record
"MBR partition entries and the MBR boot code used in commercial
operating systems, however, are limited to 32 bits.[2] Therefore, the
maximum disk size supported on disks using 512-byte sectors (whether
real or emulated) by the MBR partitioning scheme (without using
non-standard methods) is limited to 2 TiB."

That says it correctly.

--
Tim Slattery
tim at risingdove dot com