GPT Hard Disk Drives for HP Business Desktops

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GPT hard Disk Drives

For HP Desktops

April 2011

Table of Contents:

Abstract .............................................................................................................. 1

Why GPT? ........................................................................................................... 1

GPT vs MBR ........................................................................................................ 2

Bootable vs Data Drives and UEFI BIOS ................................................................ 4

OS Support ......................................................................................................... 6

Storage Driver Support ........................................................................................ 6

Imaging Tool Support for GPT .............................................................................. 7

Drive Encryption .................................................................................................. 7

Summary ............................................................................................................ 8

For more information .......................................................................................... 8

Abstract

In order to be used in a computer system, a hard disk drive (HDD) must first be

partitioned. Partitioning is done at the drive level and for many decades used the

Master Boot Record (MBR) partition method. A new method called GUID Partition

Table (GPT)) is now used for large-capacity drives. GPT allows for volume sizes

much greater than 2.19TB, and therefore must be used on drives larger than the

MBR limit of 2.19TB. This white paper describes the rationale for GPT and the types

of OS, BIOS, driver, and SW tool support needed to successfully implement GPT

drives in desktop systems.

Why GPT?

HDD areal density (bits/sq in) and tracks per inch (TPI) continue to steadily

increase. For 2010, many typical desktop 3.5” hard drives have areal densities

and TPI that permit capacities up to 500GB per platter. In 2011, it is expected that

improvements in areal density and TPI will allow drive manufacturers to begin

shipping drives that have capacities of1TB/platter. At this density, drives of 2TB

and 3TB capacities become more easily producible and hence cheaper and more

widely available.

Summary of content (8 pages)

PAGE 1
GPT hard Disk Drives For HP Desktops April 2011 Table of Contents: Abstract .............................................................................................................. 1 Why GPT?........................................................................................................... 1 GPT vs MBR ........................................................................................................ 2 Bootable vs Data Drives and UEFI BIOS .................................................
PAGE 2
For decades, MBR partitioning was sufficient to support the amount of hard drive addressing spaces known as Logical Block Addresses (LBAs) that existed on hard drives. MBR partitioning supported 32-bit addressing and, along with 48-bit LBA extensions, was able to support drives up to a limit of 2.19TB using standard 512byte sectors (or 512-byte sector emulation). However, now that hard drive sizes are beginning to exceed the 2.19TB limit, a newer approach is needed.
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Protects MBR-based disk utilities from overwriting GPT drives List of drive partition entries (up to 128) Protective MBR LBA 1 Primary GPT Header LBA 2 Entries 1 thru 4 LBA 3 Entries 5 – 128 LBA 34 Primary GPT Defines usable blocks on the disk LBA 0 Partition 1 Partition 2 Drive partitions (up to 128) Remaining Partitions LBA -34 LBA -33 Entries 5 – 128 Secondary/backup GPT header and partition entries LBA -2 LBA -1 Secondary GPT Entries 1 thru 4 Secondary GPT Header LBA = 512 bytes N
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Partition Table Master Boot Code Master Boot Code 1st Partition Table Entry 1st Partition Table Entry 2nd Partition Table Entry 2nd Partition Table Entry 3rd Partition Table Entry 3rd Partition Table Entry 4th Partition Table Entry 4th Partition Table Entry 0x55 AA 0x55 AA Primary Partition (C:) Primary GUID Partition Table Header Primary Partition (E:) Logical Drive (G:) Logical Drive (H:) Logical Drive n GUID Partition Entry 1 GUID Partition Entry 2 GUID Partition Entry n GUID Partition En
PAGE 5
The BIOS Characteristic Extension Byte #2 is described in Table 1. Bit 3 of Byte 2 specifies UEFI specification support. Table 1. BIOS Characteristics Extension Byte 2 Bit Position Description 0 When set, BIOS boot specification is supported 1 When set, function key-initiated Network Service boot is supported. When function key-initiated Network Service boot is not supported, a network option ROM may choose to offer this functionality on its own, thus offering this capability to legacy systems.
PAGE 6
Figure 4. Startup Menu OS Support 32-bit Microsoft Windows™ will not provide boot support for GPT. For HP desktops, bootable GPT drives and data storage drives will be initially supported under the Microsoft Windows 7™ SP1 64-bit OS. Bootable GPT drives can also be supported under the Microsoft Vista™ SP1 64-bit OS. Both of these operating systems require a UEFI BIOS to support a bootable GPT drive.
PAGE 7
Imaging Tool Support for GPT In generating SW boot images for GPT drives, the user must utilize “GPT aware” software tools. Not all tools will automatically support partitioning and formatting for GPT. For example, only newer versions of Symantec GHOST™ are able to handle GPT partition tables. The user will need to check the particular tool documentation to ensure the software provides support for GPT. A certain percentage of users may choose to re-install the 64-bit OS with a Microsoft DVD.
PAGE 8
Summary GPT-based hard disk drives offer a more consistent, scalable approach to formatting and partitioning hard drives. GPT allows more efficient use of the larger hard drives now becoming available, and also allows such hard drives to be a bootable part of a UEFI-based system. With GPT, partition and formatting support of ever-increasing drive sizes is assured for many more years.