AN EXPLORATION OF HARD DRIVES WITH A GUID Partition Table (GPT)

Summary:

The "GUID Partition Table" (also known as "GPT") is the computer industry's emerging replacement for the aging "Master Boot Record" ("MBR") partition table. The legacy MBR partition table cannot be used for hard drives that are larger than 2.2 Terabytes while the GPT allows for hard drives many orders of magnitude larger than 2.2 Terabytes. Like all "bleeding edge" technologies, it will bring challenges for all who must utilize the new partition table format.

BASIC INFORMATION ABOUT

GPT PARTITION TABLES FOR HARD DRIVES

See

http://www.microsoft.com/whdc/device/storage/gpt-on-x64.mspx

and

http://www.worldlingo.com/ma/enwiki/en/GUID_Partition_Table

and

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

for explanations of the structure of a hard drive that has a GPT partition table.

A GPT hard drive that is used to store data by Windows Vista or Windows 7 (but that is not bootable by Windows) has to have a "Microsoft Reserved" partition" (MSR).

A GPT hard drive that is bootable by Windows Vista or Windows 7 must have both a "EFI System Partition" (ESP) and a "Microsoft Reserved Partition" (MSR).

See 64-bit versions Windows Vista and Windows 7 can only boot from within a GPT hard drive if the motherboard/system has an "Extensible Firmware Interface" ("EFI") instead of a BIOS.

See

http://www.microsoft.com/whdc/device/storage/gpt_faq.mspx

for details.

The "Paragon GPT Loader" software application allows computers that run the 32-bit versions of "Windows XP" to access "GPT" hard drives. See

http://www.paragon-software.com/technologies/components/gpt-loader/

We will attempt to test the "Paragon GPT Loader" with "Windows XP" in the future.

Since we do not have a EFI computer to test booting up Windows with a bootable GPT hard drive, we decided to create and test GPT hard drives that store data files and folder but which are not "bootable".

We embarked on three adventures:

For "Adventure 1", we used "Windows 7" to initialize a GPT hard drive.

For "Adventure 2", we used "Parted Magic" Linux to initialize a GPT hard drive.

For "Adventure 3", we used "Windows 7" and then "Parted Magic" Linux to initialize a GPT hard drive that can be used for data storage for both Windows and Linux

ADVENTURE 1:

GPT DRIVE INITIALIZED BY "WINDOWS"

We used "Windows 7 Professional 64-bit" to initialize a hard drive with a GPT partition table instead of a MBR partition table as follows:

Step 1:

Start "Control Panel".

Step 2:

Double-click on "Computer Management".

Step 3:

Click on "Disk Management":

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Step 4:

Use the right mouse button click on the "Disk 1" square that represents the target hard drive.

Step 5:

A popup context menu was displayed:

Step 6:

One of the items on the popup context menu was "Convert to GPT Disk".

This implied that the disk currently had a "Master Boot Record" ("MBR").

Step 7:

We used the left mouse button to click on "Convert to GPT Disk":

Step 8:

Next, we used the right mouse button to click again on the square that represents the target hard drive:

Step 9:

We then clicked on "Properties" on the popup context menu:

Step 10:

Next, we clicked on the Volumes tab:

Step 11:

It shows that the hard drive has a "GPT" type of partition table.

Step 12:

We closed the "..Properties" box by clicking on the "X" button near its upper right-hand corner.

Step 13:

We returned to the "Disk Management" window.

Step 14:

We used the right mouse button to click on the "Unallocated" area of the target hard drive.

Step 15:

A popup utility menu was displayed.

The popup utility menu showed "New Simple Volume.." as a menu option:

Step 16:

We used the left mouse button to click on "New Simple Volume..".

Step 17:

A "..New Simple Volume Wizard" box was displayed:

Step 18:

We clicked on it's "Next" button.

Step 19:

A "Specify Volume Size" box was displayed:

Step 20:

We specified the desired volume size, as requested:

Step 21:

We used the left mouse button to click on the "Next" button.

Step 22:

An "Assign Drive Letter or Path" box was displayed:

Step 23:

We selected the desired drive letter.

Step 24:

Then we clicked on the "Next" button.

Step 25

A "Format Partition" box was displayed:

Step 26:

We provided a volume label:

Step 27:

We then clicked on the "Next" button.

Step 28

We repeated Steps 14 through 27 four times to create a total of 5 NTFS partitions.

Step 29:

The 5 NTFS partitions on "Disk 1" were displayed as follows:

GPT DISK INITIALIZED BY "WINDOWS 7 64-BIT" AS SEEN BY "GPARTED" IN "PARTED MAGIC"(ADVENTURE 1)

We booted the computer with the "Parted Magic" Linux LiveCD.

We started the "GParted" software application:

"GParted" displayed the Windows-formated GPT disk as 6 primary partitions with the first (left-most) partition as a small 128 Megabyte partition..

The first partition had a "Microsoft Reserved" flag "set".

If you right click on the "Microsoft Reserved" partition:

and then click on "Manage Flags":

Then, you can see that the "Microsoft Reserved" flag is set for the tiny 128 Megabyte partition at the start of the hard drive.

The "Microsoft Reserved" partition is used by Windows to support Windows-specific features such as "Dynamic Volumes". It is not used by non-Microsoft operating systems.

In Microsoft's technical literature, the "Microsoft Reserved" partition is also known as a "MSR".

In Microsoft's technical literature, the "Microsoft Reserved" partition is sometimes also called "Microsoft System Reserved" partition.

See

http://technet.microsoft.com/en-us/library/dd799232(WS.10).aspx

and

http://www.servinghistory.com/topics/Microsoft_Reserved_Partition

GPT DISK INITIALIZED BY "WINDOWS 7 64-BIT " VIEWED FROM UBUNTU 10.10 32-BIT'S "DISK UTILITY" (ADVENTURE 1)

"Ubuntu 10.10 32-bit" has a "Disk Utility" that saw all 6 partitions.

GPT DISK INITIALIZED BY "WINDOWS 7 64-BIT" FROM THE POINT OF VIEW OF "WINDOWS XP PRO 32-BIT"(ADVENTURE 1)

"Disk Management" in Windows XP Pro 32-bit can see the entire GPT disk as a single "GPT Protective Partition" but "Windows Explorer" does not allow you to see any of the partitions on the GPT hard drive:

This is one of the features of a "GPT" partition table. It uses the legacy table space of the "Master Boot Record" partition to indicate to application software and operating systems that can only read/see Master Boot Records that:

the "GPT" hard drive is a "Healthy (GPT Protective Partition),

that it is not accessible,

that it is a single partition,

and

how big the single partition is.

GPT DISK INITIALIZED BY "WINDOWS 7 64-BIT" FROM THE POINT OF VIEW OF "WINDOWS VISTA 32-BIT"(ADVENTURE 1)

"Windows Explorer" in Windows Vista 32-bit can see and write to all of the NTFS partitions.

"Disk Management" in Windows Vista 32-bit shows all of the NTFS partitions but you are not shown the "Microsoft Reserved" partition. (Apparently "Windows Vista 32-bit" hides the "Microsoft Reserved" partition from view and uses it for Windows-specific operating system functions such as "Dynamic Disks". The GPT standard does not allow for hidden partitions on a GPT disk.)

ADVENTURE 2:

GPT DRIVE INITIALIZED BY LINUX

Next, we used the "GParted" in the "Parted Magic" (Linux) LiveCD to create a GPT disk.

From within "GParted" in "Parted Magic"(Linux), this GPT hard drive looks like this:

Note that we also used "GParted" to create a 2.93 Gigabyte "Linux Swap" partition on this GPT hard drive. This partition was created to allow to facilitate the installation "Ubuntu 10.04" onto this hard drive in the future.

GPT DISK CREATED BY "GPARTED"(LINUX)

AS VIEWED FROM "UBUNTU 10.10 32-BIT" (ADVENTURE 2)

The "Disk Utility" of "Ubuntu 10.10 32-bit", correctly displays the GPT hard drive that we created with "GParted" as a single EXT4 partition:

GPT DISK CREATED BY "GPARTED"(LINUX)

AS VIEWED FROM "WINDOWS 7 PROFESSIONAL 64-BIT" (ADVENTURE 2)

When it first discovers the Linux-formated GPT hard drive, "Windows 7 Professional 64-bit" asks you if you want to "Initialize" it. Apparently "Windows 7 Professional 64-bit" does not recognize the GPT disk because it lacks a "Microsoft Reserved" partition on it.

The "Initialize Disk" dialog box gives you a choice between intializing with a "MBR" partition table or a "GPT" partition table:

We selected "GPT":

Then we clicked on the OK button:

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We then used the right mouse button to click on the "Disk 1" square:

Next we clicked on "Properties" in the popup context menu:

Next, we clicked on the "Volumes" tab of the "..Properties" box:

The Volumes tab showed that the disk had a "Partition style" of "GPT":

If you use then "GParted" on the "Parted Magic" LiveCD to view the GPT hard drive that has been RE-initialized by "Windows 7 Professional 64-bit", it shows that a 128 Megabyte "Microsoft Reserved" partition has been placed on the hard drive by "Windows 7..":

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"GParted" shows it as of an "unknown" file system with the "Microsoft Reserved" flag set.

ADVENTURE 3:

GPT HARD DRIVE THAT CAN BE USED BY BOTH WINDOWS AND LINUX FOR DATA STORAGE

To make a GPT Data Hard Drive that is usable by both Windows and Ubuntu for data storage, you can to start off by using "Disk Management" in "Windows 7" or "Windows Vista":

Start "Control Panel".

Double-click on "Administrative Tools".

Double-click on "Computer Management".

Double-click on "Disk Management".

If you have already connected a blank hard drive to your computer, an "Initialize Disk" dialog box will be displayed:

The "MBR" option is selected by default:

Select the "GPT" option:

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Click on the "OK" button:

The "Initialize Disk" box will disappear.

Use the right mouse button to perform a click on the square that represents the target drive.

In this example, we used the right mouse button to click on "Disk 1" and a popup context menu was displayed:

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Click on "Properties" in the popup context menu.

A "..Properties" box will be displayed:

Click on the "Volumes" tab.

The "Volumes" tab shows that the "Partition style" is "GUID Partition Table..":

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We discovered that all of the NTFS partitions were usable as data hard drive partitions in "Ubuntu 10.04 32-bit".

For some unknown reason, the "Disk Utility" in "Ubuntu 10.04 32-bit" was unable to create a new "ext4" partition in unallocated space in a GPT hard drive that was originally initialized by "Windows 7..".

USING "GPARTED" IN "PARTITION MAGIC" (LINUX) TO ADD AN EXT4 PARTITION TO A GPT HARD DRIVE THAT WAS ORIGINALLY INITIALIZED BY "WINDOWS 7.." (ADVENTURE 3)

Attach the hard drive to your computer and boot up with the "Parted Magic" LiveCD.

Start "GParted":

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Use the right mouse button to click in "unallocated" space.

A popup context menu will be displayed:

Click on "New:

A "Create New Partition" box will be shown:

Select the desired size for the new partition.

If it is not already selected, select "ext4" for the "File System".

Click on the "Add" button:

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The "Create New Partition" box will disappear:

Click on the "Apply" button.

An "Applying Pending Operations" box will be displayed:

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Click on the "Close" button when you are notified that "All operations successfully completed":

The net result is that this hard drive was initialized by "Windows 7" wigth a GPT; then GParted of "Parted Magic"(Linux) was used to add an EXT4 partition to it:

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When this hard drive was re-connected to a Windows 7.. computer, the Windows 7 computer sees the EXT4 partition as a "RAW" partition and does a drive letter to it:

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When this hard drive was attached to a Ubuntu 10.04 computer, all of NTFS partitions and the single EXT4 partition are accessible, as shown when you click on "Places":

In our example, the EXT4 partition is shown as "839 GB Filesystem" because we forgot to assign it at "partition label" when we created it with "GParted".

To see more:

Click on "System":

Click on "Administration".

Click on "Disk Utility":

A "Disk Utility" window will be displayed:

In this example, we then clicked on "2.0 TB Hard Disk", our GPT hard drive:

As expected, Ubuntu was unable to access the "Microsoft Reserved" partition of the GPT hard drive which is shown as a 134 Megabyte partition of "Unknown" format.

Ubuntu was able to access all 5 NTFS partitions and the unlabeled 839 EXT4 partition.

LESSONS LEARNED FROM ADVENTURES 1 THROUGH 3

LESSON 1:

We discovered that you cannot use "GParted"(Linux) to make a "Microsoft Reserved" partition for a GPT hard drive.

LESSON 2:

DETAILS ABOUT THE "MICROSOFT RESERVED" PARTITION IN A GPT HARD DRIVE IN "WINDOWS 7"

The "Microsoft Reserved" partition in a GPT hard drive that has been initialized by "Windows 7" has the following features:

Does not have a partition "label".

Has it's "Microsoft Reserved" flag set.

Is 128 Megabytes in size.

Is not displayed in "Disk Management" of "Windows 7.."

Cannot be removed.

GParted of "Parted Magic" shows it as a partition with an "Unknown" format.

LESSON 3:

DETAILS ABOUT THE

"SYSTEM RESERVED" PARTITION IN A MBR HARD DRIVE IN "WINDOWS 7"

Has by default a partition "label" of "System Reserved".

Has a flag of "Boot" set.

Is 100 Megabytes in size.

Is displayed in "Disk Management" of "Windows 7.."

Can be removed with a repair procedure involving the installation media DVD.

GParted of "Parted Magic" shows it as an NTFS partition.

If you install "Windows 7" into a blank MBR hard drive,

the hard drive where "Windows 7" Professional installed itself originally looks like this:

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The "System Reserved" partition in a MBR hard drive is optional. It has a label of "System Reserved" and a flag of "boot". While it is installed by default by the "Windows installation process", you can delete it and then use boot up the computer with the "Windows installation media" DVD

and then use "Repair" and "System Recovery Options" to merge the functions of the "System Reserved" partition into your C: drive.

LESSON 4:

FLAG DIFFERENCES BETWEEN MBR AND GPT HARD DRIVES

MBR and GPT hard drives do not use the same "flags" for partitions:

The flags for partitions in a MBR drive:

The different set of flags in a GPT hard drive:

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A side-by-side comparison of GPT and MGR flags:

Flags for Partitions in a GPT HD:

Flags for Partitions in a MBR HD: