Is it possible to have GUID and MBR in one external hdd?

anyone knows how the best solution to have them carried by two partition scheme - GUID and MBR in TWO different partition - on ONE disk?

None. Unlike partitions, a drive can only have one partition scheme.

You may want to install MacDrive into Windows and format the whole drive to Mac OS Extended.

(56354)

The partition scheme is only relevant if you want a disk to be bootable and as in your case you want it bootable by only OS X there isn't a problem and you should use GUID. The second partition will be readable by Windows regardless, as long as it's in a format that windows understands of course.

First of GUID (GPT) is not a partition type, it is a Partition scheme. It involves a 200mb special
partition (known as an EFI partition) that allows communication between a computer's firmware
and an msdos bios (mbr) partition. An HFS (Apple) volume does not need GPT to boot. GPT is
needed only for booting msdos or other OS that is bios dependent.

Read about it here:
http://developer.apple.com/library/mac/#technotes/tn2006/tn2166.html

The short version:
A GPT drive can support both APM (Apple) and MsDos volumes on the same drive,
however, GPT should not be used with drives that will be read by windows versions
earlier than XP SP2, as they do not understand GPT, and may overwrite GPT partition
information.

more GPT stuff:
http://en.wikipedia.org/wiki/GUIDPartitionTable

GPT is not needed on drives that have no bios bootable (mbr) and no bootable Mac partitions
(data only drives).

Kj

KJK555 wrote:
GPT is needed only for booting msdos or other OS that is bios dependent.

Well that would seem to contradict the explanation given by Disk Utility wouldn't it?

GUID Partition Table:
To use the disk to *start up* an Intel-based Mac, or to use the disk as a non-startup disk with any Mac with Mac OS X version 10.4 or later.

Edit
Ah, I see from the tech note that Intel-based Macs can still boot from APM but that Apple doesn't support it. I still find your choice of words puzzling though.

Message was edited by: ajduguid

Hi ajduguid:
Didn't mean to confuse anyone, but the Apple GUID issue is misunderstood because of the way
Apple implements its use is a bit confusing.
http://www.miscfits.com/2008/01/apples-bootcamp-bungles-gpt.html

At the moment, the only thing Apple really uses GPT for is to boot msdos systems, they do not
need the EFI volume to communicate with OS X during boot time, because OS X does not
require bios and/or a master boot record (mbr) to boot. OS X keeps it's booting info in the
/System/Library/CoreServices/boot.efi (Intel Macs) and/or bootX (PPC).

When hard drives become too large (>2 TB) to Support Apple Partition Map Scheme (APM),
then GPT will be required to boot a Mac, as the firmware will need the info stored in the EFI
partition to find the starting location of the Mac boot volume(s). So that's why Apple is dropping
support for booting off APM disks. They are indeed looking to the future.

Most modern OS's support GPT, but many older ones do not. Dos, windows 3.x,95, 98, NT3.5-4.0,
OS/2, etc. cannot deal with GPT. I know most of those relics are retired or running in virtual
machines (such as parallels desktop), but those that are not should not be used with GPT disks,
as they may destroy the partition mapping.

APM is sometimes a good choice for multiple volume data (non bootable) drives, particularly
for sharing Data space with an older OS like Windows 2000. Simply split the disk (using disk utility)
into two or more volumes, format the Apple volumes with DU, and leave the others unformatted
if you want ntfs. Hook up the drive to windows 2000 and format the empty partition(s) as (a) logical
volume(s) using windows disk manager.

Here's more reading for those want more partitioning info:
http://en.wikipedia.org/wiki/ApplePartitionMap

http://en.wikipedia.org/wiki/BootCamp(software)

http://en.wikipedia.org/wiki/Listof_disk_partitioningsoftware

http://en.wikipedia.org/wiki/Masterbootrecord

http://en.wikipedia.org/wiki/Disk_formatting

http://www.mactech.com/articles/mactech/Vol.23/23.03/APMtoGPT/index.html

http://en.wikipedia.org/wiki/Booting

http://en.wikipedia.org/wiki/ExtensibleFirmwareInterface

http://en.wikipedia.org/wiki/File_system

http://www.macgeekery.com/tips/troubleshooting/whenthe_boot_camp_assistantfails

So in answer to the OP's question, no you can't have separate GUID and MBR partitions on
the same drive, as the GUID and MBR would be fighting over sector 0 at the beginning
of the drive. Apple's GUID allows the use of an MBR partition (included within in the GPT)
on a firmware equipped Mac, with the EFI and the firmware creating the bios emulation
needed to boot Windows. An MsDos data logical partition, in contrast, can easily be seen
and used by both Windows and Mac in a GUID (GPT) setup, when both OS's are GPT aware
such as OS X 10.4.x or greater and XP SP2 and greater.

In other words, late model Windows machines can read MsDos formatted volumes on Apple
GPT formatted disks just fine. Can they boot from them? Well, not directly, since that requires
the proper firmware, but Windows can boot logical drives as long as windows boot manager
is sitting somewhere on a mbr equipped primary partition, such as a secondary drive.

As the old saying goes: "where there is a will, there is a way" definitely applies to disk
partitioning. Most of Apple's disk utilities partitioning rules can easily by broken or
worked around or completely overcome using third party software such as iPartition
and other such similar products.
http://www.coriolis-systems.com/iPartition.php

Kj