Datasheet

IBM�Japan�Hardware�Announcement IBM�is�a�registered�trademark�of�International�Business�Machines�Corporation

Enterprise�drives�have�much�higher�write�endurance�and�as�a�result�can�withstand�a

greater�number�of�writes�over�the�lifetime�of�the�device�compared�to�enterprise�value

level�drives.�SSD�write�endurance�is�an�important�factor�to�consider�because�unlike

spinning�disk�media,�NAND�flash�has�a�finite�number�of�program/erase�cycles�it�will

accept.�SSD�write�endurance�is�typically�measured�by�the�number�of�program/erase

cycles,�or�P/E�cycles,�each�cell�incurs�over�its�lifetime,�and�per�drive�is�listed�as

TBW�in�the�drive�specification.�This�statistic�can�be�used�to�give�an�estimate�of�the

drive's�remaining�life�based�on�the�workload�to�which�the�drive�will�be�subjected.

The�TBW�value�assigned�to�a�solid-state�drive�is�the�total�bytes�of�written�data

(based�on�number�of�P/E�cycles)�a�drive�can�be�guaranteed�to�complete.�Reaching�this

limit�does�not�cause�the�drive�to�immediately�fail;�it�simply�denotes�the�maximum

number�of�writes�that�can�be�guaranteed.

A�solid-state�drive�will�not�fail�upon�reaching�the�specified�TBW.�At�some�point

based�on�manufacturing�variance�margin,�after�surpassing�the�TBW�value,�the�drive

will�reach�the�end-of-life�point,�at�which�the�drive�will�go�into�a�read-only�mode.

As�a�result�of�the�technology�limitations,�care�must�be�taken�to�use�SSDs�in

environments�that�will�not�exceed�the�TBW�of�the�drive�prior�to�the�required�life

expectancy�of�the�application.

As�an�example,�assume�an�access�pattern�of�50%�random�data�and�50%�sequential�data

with�block�size�mixes�of�5%�of�the�data�is�4k�block�size,�5%�of�the�data�is�8k�block

size,�10%�of�the�data�is�16k�block�size,�35%�of�the�data�is�64k�block�size,�and�35%

of�the�data�is�128k�block�size.�For�a�drive�capable�of�72�TB�of�lifetime�writes,

assuming�an�approximation�of�the�workload�stated�above�as�being�worst�case,�the�drive

workload�must�be�limited�to�no�more�than�40�GB�of�writes�per�day�to�last�five�years

and�stay�inside�the�72�TBW�limit.�For�the�device�to�last�threes�years,�the�drive

write�workload�must�be�limited�to�no�more�than�65�GB�of�writes�per�day.

Additional�information�is�available�at

http://www-03.ibm.com/systems/x/options/storage/solidstate/index.html

Solid-state�memory�cells�have�an�intrinsic,�finite�number�of�program/erase�cycles

that�each�cell�can�incur.�As�a�result,�each�solid-state�device�has�a�maximum�amount

of�program/erase�cycles�to�which�it�can�be�subjected,�documented�as�TBW�or�Drive

Writes�Per�Day�(DWPD).�IBM's�warranty�for�the�device�is�limited�to�drives�that�have

not�reached�the�maximum�guaranteed�number�of�program/erase�cycles,�as�stated�below.�A

drive�that�reaches�this�limit�may�fail�to�operate�according�to�its�specifications.

Maximum�warranted�drive�writes�per�drive�is�2.39�Full�Drive�Writes�per�day�for�five

years�or�0.5�PB�TBW�on�the�1.8-inch,�2,5-inch,�3.5-inch,�SSD�for�Flex�x222,�and�SSD

for�NeXtScale�120�GB�SATA�SSD�depending�on�workload�and�data�patterns.

Maximum�warranted�drive�writes�per�drive�is�2.39�Full�Drive�Writes�per�day�for�five

years�or�1.0�PB�TBW�on�the�1.8-inch,�2.5-inch,�3.5-inch,�SSD�for�Flex�x222,�and�SSD

for�NeXtScale�240�GB�SATA�SSD�depending�on�workload�and�data�patterns.

Maximum�warranted�drive�writes�per�drive�is�2.27�Full�Drive�Writes�per�day�for�five

years�or�1.9�PB�TBW�on�the�1.8-inch,�2.5-inch,�3.5-inch,�SSD�for�Flex�x222,�and�SSD

for�NeXtScale�480�GB�SATA�SSD�depending�on�workload�and�data�patterns.

Maximum�warranted�drive�writes�per�drive�is�1.36�Full�Drive�Writes�per�day�for�five

years�or�1.9�PB�TBW�on�the�1.8-inch,�2.5-inch,�3.5-inch,�SSD�for�Flex�x222,�and�SSD

for�NeXtScale�800�GB�SATA�SSD�depending�on�workload�and�data�patterns.