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Home , BIOS, GUID Partition Table, Master boot record

FAQ: Drive Partition Limits

What is the 2.2TB limitation? How will BIOS and OS address this limit? Users upgrading a system with a The UEFI specification defines a new model for larger may have problems using the between personal-computer more than 2.2 terabytes (TB) of disk space. operating systems and platform , This limit arises from the maximum size of the (MBR) partitioning method updating BIOS interfaces such as MBR. used by most personal . UEFI supports the GUID Partition Table (GPT), This document explains the issue and a more flexible partitioning scheme. GPT disks discusses long term solutions based on GPT use 64-bit values to describe partitions, allowing and Unified EFI (UEFI) specifications. larger partitions. GPT also fixes other issues Why does this limitation exist? related to MBR (data integrity, tables, This limitation dates back to the 1980s and the maximum number of partitions, …). original IBM PC. This introduced the master Using 64-bit values, GPT can handle disks of up boot record (MBR) partitioning scheme to to 9.4 x 1021 or 9.4 zettabytes (ZB). describe hard disk partitions. Will the OS boot to a partition over 2.2TB? BIOS systems with MBR disks use 32-bit values to describe the starting offset and length of a Only operating systems supporting UEFI and partition. Due to this size limit, MBR allows a GPT are expected to boot from partitions larger maximum disk size of approximately 2.2 TB and than 2.2TB. This also requires the underlying a maximum of four primary partitions. firmware to implement UEFI. How does this affect today’s computers? and already support UEFI in To meet the demands of modern computer newer OS revisions. Microsoft has published users, hard disk drive manufacturers will several documents related to UEFI & GPT: produce disks in excess of 2 TB in 2010. Users • Windows and GPT FAQ [Microsoft WHDC] UEFI Forum upgrading a computer system by adding or 3855 SW 153rd Drive replacing an existing hard disk drive with a • UEFI and Windows [Microsoft WHDC] Beaverton, OR 97006 USA larger drive may encounter problems using What other benefits does UEFI bring? more than 2.2 TB of disk space. Tel: +1 503-619-0864 For more information on UEFI, check out the Fax: +1 503-644-6708 specifications posted at www.uefi.org [email protected] www.uefi.org ©2010 UEFI Forum – www.uefi.org