Dell PowerEdge R530 User Manual
512e and 4Kn Disk Formats
This paper 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
December 2013
A Dell Technical White Paper
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2 512e and 4Kn Disk Formats
Contents
1 Overview ......................................................................................................................................................................................... 4
2 Background ..................................................................................................................................................................................... 5
3 The long-term benefit of 4K sectors ........................................................................................................................................ 6
4 Understanding the impacts of the 4K transition..................................................................................................................... 6
4.1 512-byte sector emulation ............................................................................................................................................... 6
4.2 Small or runt writes ............................................................................................................................................................ 8
4.3 Mixing drives ........................................................................................................................................................................ 9
5 Preparing for and managing the 4K transition ........................................................................................................................ 9
5.1 Managing 4K sectors in the Windows environment ................................................................................................... 9
5.2 Enterprise Windows support for 4K sector media ...................................................................................................... 9
5.3 Managing 4K sectors in the Linux environment ........................................................................................................ 10
5.4 VMware support ............................................................................................................................................................... 10
5.5 Dealing with unaligned conditions ................................................................................................................................ 11
5.6 512e/4Kn application support ........................................................................................................................................ 11
6 Drive labels ..................................................................................................................................................................................... 11
7 Conclusion ..................................................................................................................................................................................... 12
8 Additional resources .................................................................................................................................................................... 12
3 512e and 4Kn Disk Formats
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 is quickly ramping up efforts to transition to a new type of format for
media, known as Advanced Format, which has a 4KB physical sector size. This change brings two new
types of media to the enterprise market:
• 4KB"native:"This "m e dia"has "n o "emulation"laye r"and"directly"exposes"4 KB"as"its"logi c al"and"physical"
sec to r"size . "T he"overa ll"issu e "with"this"ne w"type "o f"media"is "that"the"majo r ity"o f"curre n t"and"legacy"
applications"and"o p erating"syste m s "do"not"query"fo r"and"align"I/O s "to"the "p hysical"sector"size,"
which"can"result"in"unexpected"failed"I/Os.
• 512-byte"em ulation"(512e): "T his"media"has"an"emulation"function"and"exposes"512"bytes"as"its"
lo gical"se c tor"size "(simila r"to"a"regular"disk"today),"but"m akes"its "physical"sector"size"info rmation"
(4 KB)"available."The"ove rall"is sue"with"thi s"new"ty pe"of"media"is"tha t"the "m a jority"of"app lications"and"
operating"systems"do"not"understand"the"existence "of"the"p hysical"s ec tor"size,"whic h "c an"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
IDEMA
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 paper 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.
(The International Disk Drive Equipment and Materials Association). Enterprise HDDs are also
4 512e and 4Kn Disk Formats
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