by Zsolt Kerekes,
editor - StorageSearch.com
first published in 2000
A solid state disk / drive (SSD) -
is electrically, mechanically and software compatible with a conventional
(magnetic)
hard disk.
The
difference is that the storage medium is not magnetic (like a hard disk) or
optical (like a CD) but
solid state
semiconductor such as
battery backed RAM, RRAM,
PRAM or other electrically erasable RAMlike non volatile memory chip such as
flash.
This provides faster access time than a hard disk, because the SSD
data can be randomly accessed in the same time whatever the storage location.
The SSD access time does not depend on a read/write interface head
synchronising with a data sector on a rotating disk. The SSD also provides
greater physical resilience to physical vibration, shock and extreme temperature
fluctuations. SSDs are also imune to strong magnetic fields which could
sanitize a hard
drive.
The only downside to SSDs is a higher
cost per megabyte of
storage - although in some applications the higher
reliability of SSDs
makes them cheaper to own than replacing multiple failing hard disks. When the
storage capacity needed by the application is small (as in some embedded
systems) the SSD can actually be cheaper to buy because hard disk oems no
longer make low capacity drives. Also in enterprise server acceleration
applications - the benefit of the SSD is that it reduces the number of servers
needed compared to using hard disk based
RAID on its own.
Historically
RAM based SSDs were
originally faster than
flash based products -
but flash became the dominant memory in enterprise SSDs as a result of
successive improvements in architecture during 2004 to 2015. (See
sugaring flash
for the enterprise for details.)
The reasons that users might
benefit from buying SSDs are listed in the
SSD Market
Adoption Model.
Implicit in all my usages of the term "flash
SSD" is the assumption that the device includes some form of
controller which
performs wear-leveling - as opposed to less smart flash memory storage which
doesn't.
News about SSDs and a directory of all market active SSD oems can be
seen on STORAGEsearch.com's main
SSD page.
For
other SSD related terms see -
flash SSD Jargon.
Most of this definition (above) by STORAGEsearch.com was first
published in 2000. |
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here are some more SSD
articles
the SSD story 1973 - 2017
2013 -
SSD market changes
2014 -
SSD market changes
2015 - SSD market
changes
2016 -
SSD market changes
SSD futures? - list of
market analysts etc | |
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In 2015, we put together a
series of articles covering Solid State Drive technology, building from a single
NAND cell to packaging, controller functions and SSD characteristics. |
SSD
101 - an educational series for industrial system designers by
Cactus Technologies | | |
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