Partitioning GPT Disks on UEFI systems

Tom’s Hardware (December 30, 2009 by Patrick Schmid and Achim Roos)

“You need a 64-bit version of Windows XP Professional (with the same core operating system version as Windows Server 2003 SP1), Vista, or Windows 7, to get full GPT support for drives that offer more than 2TB capacity. GPT offers the following features:

  • Maximum raw partition capacity of 18 exabytes
  • The Windows NTFS file system is limited to 256TB each: with up to 2^64 logical blocks in length and a physical cluster size of 65536-bytes (formatting with an allocation unit of 64 KiB sector groups required!)
  • Implementation restriction of 128 partitions per disk (limited by the amount of space reserved for partition entries in the GPT)
  • Primary and backup partition tables available for redundancy
  • Well-defined and self-identifying partition format
  • Each partition has a unique ID to avoid identifier collisions (“GUID” partition table)

Here is an overview of your possible partitioning options and actions on GPT and MBR:

32-bit Windows 64-bit Windows
GPT MBR GPT MBR
Boot No Yes Yes No
Read No Yes Yes Yes
Write No Yes Yes Yes

UEFI support becomes relevant for drives >2TB. It must be present to enable booting from such large partitions provided the other prerequisites (64-bit Windows and GPT) are met.

GPT Details on Windows x64
GPT will automatically install the EFI System Partition (ESP), which contains the boot loader, EFI drivers, and all other necessary files for booting the system (such as boot.ini, HAL, and NT Loader). It utilizes the GUID Partition Table rather than the master boot record. The ESP is 1% of the drive capacity, or a minimum size of 100MB and a maximum size of 1,000MB.

GPT systems will also be equipped with an MSR partition, which stands for Microsoft Reserved. Since GPT partitions don’t allow hidden sectors, Windows utilizes this reserved space for operating system use. If you decide to convert a basic disk into a dynamic disk, Windows will use the MSR partition, shrink its size, and create the dynamic disk database using available space. On drives smaller than 16GB, the MSR partition will be only 32MB. For larger disks, it will consume 128MB.”

Chatwin says: Even if your system is GPT-compliant and created using the necessary partition, you will still need UEFI support to be able to boot from a large volume (UEFI = Unified Extensible Firmware Interface).

In the second place support for 48bit LBA also requires Advanced Format CDB block re-alignment, enabled with an internal PCI-E Host Bus Adapter Card (by using the native Windows AHCI drivers only), your RAID controller and/or HDD device drivers. Here is where Long LBA addressing comes in…

Long LBA addressing increases the number of bytes used to define the LBA in the Command Descriptor Block (CDB). System must support at least 16-byte Command Descriptor Blocks (CDBs) or 32 bytes (Protection Information commands only) and Dynamic Sense Data to access the LBA counts above 2.1TB. Eight LBA address bytes are provided in 16- and 32-byte CDBs. This is a doubling of the 4 bytes in 10-byte commands (http://www.seagate.com/docs/pdf/whit…_readiness.pdf).

Installation requirements
1. Windows XP Professional with SP2 for Windows Server 2003 64-bit, Vista 64-bit, Windows 7 64-bit for GPT.
2. UEFI booting support since Windows Vista with Service Pack 1 (64-bit only).
3. Motherboard with UEFI 2.x implementation for boot drives on a partition larger than 2.2 TB.
4. Windows 7 (SP1) is supposed to understand AF drives, and correctly aligns partitions. Without the updates in a hotfix, Windows can’t detect the drive’s physical sector size, and Windows Update (and some other features) fail. Microsoft explanation and hotfix link: An update that improves the compatibility of Windows 7 and Windows Server 2008 R2 with Advanced Format Disks is available.
5. SP1 with hotfix aren’t correctly updating the storage driver, so it can’t report sector size to Windows. The clue here is that fsutil still reports “bytes per physical sector” as “<Not Supported>”. You can fix this issue to manually install the latest Intel driver (9.6 or later): Intel® Rapid Storage Technology.
6. Alignment instructions for installing XP64:

  • Use LSoft Active Boot Disk Suite (based on WinPE 3.1) to create a partition with an offset of 2048KB, format with 4K sectors and reboot.
  • Replace with XP64 SP2 installation DVD and install without altering the partition parameters.
  • After final installation reboot and use Paragon Partition Manager Server (WinPE 3.0 recovery environment) to convert cluster size from 4KB to 64KB.
  • Shutdown and start from primary HDD partition.

Paragon just introduces a new solution: Migrate to UEFI.
“It’s a simple four-step Copy Hard Disk Wizard that transfers a 64-bit Windows Vista/7 initially installed on an MBR disk in the BIOS mode to a GPT disk and the UEFI mode, thus opening up all benefits of the GPT+UEFI configuration, including support of a high-capacity 2.2TB+ hard drive for use as the primary system HDD.

Become an early adopter and download this component for free>>

Home and small-office users who try to move their 64-bit Windows Vista or Windows 7 software environments from the dated MBR/BIOS configuration to a modern GPT/UEFI platform find that you can’t just change the partitioning scheme and enable UEFI without reinstalling the operating system from scratch. The problem is that Windows Disk Management supports conversion to GPT for empty drives only, so you’ve got no way of converting the system drive to GPT without losing data. Besides Windows Management tools do not provide an option to adjust boot files for UEFI, making it impossible for users transferring established data or system components within a single computer directly from a BIOS boot mode to a UEFI-based mode.

Paragon Migrate to UEFI can help you tackle both issues with minimal effort. Some important benefits:

  • Automatically adjusts Windows OS to start up in the UEFI mode
  • Automatically creates a GPT partitioning scheme during migration
  • Supports AFD (Advanced Format Drive) disks (mixed 512B/4K sector scheme only, including virtual)
  • The source system remains intact and can be loaded in the BIOS mode at any time
  • Copy operation is run without the system restart by employing Microsoft VSS technology”

3TB Hard Disk Utilities

Support for Disk Drives Beyond 2.2 TeraBytes (TB) and 4K Advanced Format Sectors (Seagate Knowledge Base, ©2010 Seagate Technology LLC)

“Most legacy systems built before 2011 have a traditional PC BIOS. This type of BIOS uses a Master Boot Record (MBR). The MBR Partitions can define a disk drive capacity up to 2.2TB. Windows operating systems that boot from an MBR are therefore limited to 2.2TB per MBR. A 3TB disk drive in a legacy BIOS and Window system will need a DiscWizard device driver to access the full capacity of a 3TB disk drive. Two partitions will be necessary because of the MBR limitation. The device driver mounts the capacity above 2.2TB with another MBR which looks to the system as a second virtual “physical” device.

PCWorld: The problem with deploying 3TB drives relates to older PCs (those more than a few months old, in most cases), and stems from the formula 2^32*512=2,199,023,255,552, or 2.2TB – a hard-drive addressing scheme found in legacy BIOSs and operating systems. In that formula, 2 indicates binary, 32 is the number of bits allowed in a legacy disk address, and 512 is the number of bytes in a legacy hard-drive data block. If the BIOS, drivers, I/O card, or operating system in your PC still plays by rules that involve this formula, you’ll have issues installing and using a 3TB drive.

This situation could have been avoided if the entire computer industry had future-proofed after enduring the 137GB (28-bit) limit problems that cropped up around the turn of the millennium. In truth, most vendors did, with the notable exception of Microsoft. The company chose not to implement support for anything larger than 2.2TB drives in any of its 32-bit consumer operating systems – including Windows 7.

Installing a 3TB Drive: Note that NTFS is limited to 2^32 clusters, also known as groups of sectors. That means you must format the drive with at least 1024-byte clusters, or you’ll fall prey to the formula I talked about earlier. The default is 4096, which allows up to 16TB; however, converting FAT partitions to NTFS often results in 512-byte clusters. If you’re trying to move a FAT partition to your new drive–don’t. You’re better off creating a new partition, reinstalling the OS, and restoring the files you backed up (it’s always wise to back up before doing any partitioning operations). This is because the FAT partition will in all likelihood be misaligned with the Advanced Format of your new drive.
Tip: With drivers or programs that don’t allow a full 3TB partition, you can use Windows dynamic volumes to combine two partitions into a single drive letter.

Windows Vista and Windows 7 introduced a new partition-table scheme, dubbed GPT (for GUID Partition Table). The GPT blasted past the previous limitations by supporting up to 8 zettabytes.(2^64 sectors, which, when using 512 bytes per sector, equates to 8 zettabytes). For perspective, consider that 1024 terabytes equal 1 petabyte, 1024 petabytes equal 1 exabyte, and 1024 exabytes equal 1 zettabyte.

Though not strictly a 3TB issue, all of the shipping 3TB hard drives also use Advanced Format, a low-level storage scheme employed on newer drives. AF uses larger 4KB data sectors, an approach that improves performance and diminishes the number of addresses required for any given amount of data. If you transfer legacy partitions via image backups to an AF drive, or if you format an AF drive with XP, the older 512-byte sectors might not align correctly with the new scheme.

UEFI BIOS desktop systems are new since 2011. Windows 7 64-bit and Vista 64-bit operating systems support booting from UEFI and GPT without the need of a non-Microsoft device driver. This is the Windows native solution for booting a 3TB drive to a single partition.

Quick facts about Windows and 3TB drives:

  • Windows 7 and Vista support GPT 3TB single partitions.
  • Windows 7 and Vista can only boot GPT on systems with UEFI BIOS.
  • Windows 7 and Vista can mount a GPT non-booting data drive.
  • Intel RST device drivers before v10.1 do not support 3TB disk drives.
  • Windows systems with Legacy BIOS and MBR boot drives are limited to 2.2TB partitions.
  • Windows XP x32 does not support GPT. Windows XP x64 edition can use GPT disks for data only. Only Windows XP for Itanium-based systems can boot from GPT partitions.
  • While 32-bit Windows XP systems can’t handle GPT natively, there is a solution: Paragon Software Group’s Paragon GPT Loader, that allows you to to utilize all 3TB in a single data partition.
  • DiscWizard software (Acronis®) can install a device driver which opens the full capacity of a 3TB. You can use it to create a second partition for the capacity above 2.2TB.
    DiscWizard v13 with support for 3TB drives is now available.

DiscWizard v11 for Windows is available today for all lower capacities. Click here to access DiscWizard v11.”

Overview for the best free disk imaging programs (Gizmo):

  1. Acronis for Seagate/Maxtor HDDs http://www.seagate.com/www/en-us/support/downloads/discwizard
  2. Acronis for Western Digital HDDs http://support.wdc.com/product/downloaddetail.asp?swid=119
  3. 1-Click Restore Free http://www.keriver.com/oneclick_free.html
  4. Comodo Backup http://backup.comodo.com/
  5. Drive Image XML http://www.runtime.org/driveimage-xml.htm
  6. PING http://ping.windowsdream.com/
  7. Clonezilla http://clonezilla.org/
  8. Paragon Backup and Recovery 2010 http://www.paragon-software.com/home/br-free/
  9. O&O DiskImage 4 Express Edition http://www.oo-software.com/home/en/products/oodiskimageexpress/
  10. Macrium http://www.macrium.com/reflectfree.asp
  11. EASEUS http://www.todo-backup.com/business/free-backup.htm
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