Dell PowerEdge R530 - Manual (Page 4)

4 512e and 4Kn Disk Formats
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"media"has"no"emulation"layer"and"directly"exposes"4KB"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"
(4KB)"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
Format type Bytes per sector value Bytes per physical sector value
512n 512 512
512e 512 4,096
4Kn 4,096 4,096
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 (The International Disk Drive Equipment and Materials Association). 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 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.