Dell PowerEdge C4130 User Manual
512e and 4Kn Disk Formats
This whitepaper provides the context for 512e and 4Kn disk
format migration, as well as pointing out the long-term benefits
to customers and potential pitfalls to avoid when moving from
512-byte to 4K sector formats.
Dell Engineering
May 2015
Author: Chetan Kumar, Dell Enterprise Disk Engineering
A Dell Technical White Paper
FOR INFORMATIONAL PURPOSES ONLY, AND MAY CONTAIN TYPOGRAPHICAL ERRORS AND TECHNICAL
INACCURACIES. THE CONTENT IS PROVIDED AS IS, WITHOUT EXPRESS OR IMPLIED WARRANTIES OF ANY KIND.
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Performance of network reference architectures discussed in this document may vary with differing deployment
conditions, network loads, and the like. Third party products may be included in reference architectures for the
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Trademarks used in this text:
Dell™, the Dell logo, Dell Boomi™, Dell Precision™ ,OptiPlex™, Latitude™, PowerEdge™, PowerVault™,
PowerConnect™, OpenManage™, EqualLogic™, Compellent™, KACE™, FlexAddress™, Force10™ and Vostro™ are
trademarks of Dell Inc. Other Dell trademarks may be used in this document. Cisco Nexus®, Cisco MDS®, Cisco NX0S®, and other Cisco Catalyst® are registered trademarks of Cisco System Inc. EMC VNX®, and EMC Unisphere® are
registered trademarks of EMC Corporation. Intel®, Pentium®, Xeon®, Core® and Celeron® are registered trademarks
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interest in the marks and names of others.
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Contents
1 Overview...................................................................................................................................................................................... 5
2 Background ................................................................................................................................................................................. 6
3 Long-term benefits of 4K sectors ........................................................................................................................................... 6
4 Understanding the impacts of the 4K transition .................................................................................................................. 7
4.1 512-byte sector emulation ............................................................................................................................................ 7
4.2 Small or runt writes ........................................................................................................................................................ 11
4.3 Mixing drives ................................................................................................................................................................... 11
5 Preparing for and managing the 4K transition .................................................................................................................... 11
5.1 Managing 4K sectors in the Windows environment ................................................................................................ 11
5.2 Enterprise Windows support for 4K sector media ................................................................................................... 11
5.3 Managing 4K sectors in the Linux environment ...................................................................................................... 12
5.4 VMware support ............................................................................................................................................................ 13
5.5 Dealing with unaligned conditions ............................................................................................................................ 13
5.6 512e/4Kn application support ..................................................................................................................................... 13
6 Drive labels ................................................................................................................................................................................ 13
7 Conclusion ................................................................................................................................................................................ 14
8 Additional resources ................................................................................................................................................................ 14
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Format type
Bytes per sector value
Bytes per physical sector value
512n
512
512
512e
512
4,096
4Kn
4,096
4,096
1 Overview
A change is coming in the hard drive industry. As storage densities dramatically increase, one of the most
elemental aspects of hard drive design — the logical block format size known as a sector has remained
constant. The storage industry has transitioned over to a new type of format for media, known as
Advanced Format, which has a 4 KB physical sector size. This change brings two new types of media to
the enterprise market:
4 KB native: This media has no emulation layer and directly exposes 4 KB as its logical and physical
sector size. The overall issue with this new type of media is that the majority of current and legacy
applications and operating systems do not query for and align I/Os to the physical sector size,
which can result in unexpected failed I/Os.
512-byte emulation (512e): This media has an emulation function and exposes 512 bytes as its
logical sector size (similar to a regular disk today), but makes its physical sector size information (4
KB) available. The overall issue with this new type of media is that the majority of applications and
operating systems do not understand the existence of the physical sector size, which can result in a
number of issues.
Table 1 Format types
Beginning in late 2009, accelerating in 2010, and hitting mainstream in 2011 for client-based HDDs, hard
drive companies began migrating away from the legacy sector size of 512 bytes to a larger, more efficient
sector size of 4,096 bytes, generally referred to as 4K sectors, and now referred to as Advanced Format by
The International Disk Drive Equipment and Materials Association (IDEMA). Enterprise HDDs are also
moving to this format, but are slower in adoption. The first Advanced Format enterprise HDD became
available in 2012, with a limited set in 2013 and a more general distribution in 2014.
This provides the context for this migration, as well as the long-term benefits and potential pitfalls to avoid
when moving from 512 bytes to 4K sectors.
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