Dell PowerEdge R220 512e and 4Kn Disk Formats - Page 4

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 512n 512e 4Kn Bytes per sector value 512 512 4,096 Bytes per physical sector value 512 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. 4 512e and 4Kn Disk Formats