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the SSD Buyers Guide - click to see article
SSD buyers guide ...
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SSD jargon explained
SSD jargon ..
the fastest SSDs - click to read article
the fastest SSDs ..
SSD myths - write endurance
SSD endurance ..
There are lots of different types of SSDs,
as you can see by clicking on the
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SSD controller chips 1.0" SSDs 1.8" SSDs notebook SSDs 2.5" SSDs 3.5" SSDs rackmount SSDs SAS SSDs
SSDs all flash SSDs RAM SSDs hybrid SSDs fast purge SSDs FC SAN SSDs PCIe SSDs SATA SSDs

What's an SSD?

by Zsolt Kerekes, editor - 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 faster than flash based products - but in recent years the performance of the fastest flash SSDs has been more than fast enough to replace RAM based systems in 97% of server acceleration applications.

Both types of SSDs have been available in a wide range of form factors and supporting traditional disk interfaces. A complete list of manufacturers with tables by form factor, technology type and interface type is updated in real-time in the Solid State Disks Buyers Guide

The reasons that users might benefit from buying SSDs are listed in the SSD Market Adoption Model

Take the case of SSD speedup in servers. One way of thinking about this concept in computer architecture is - SSD CPU Equivalency. For a wide range of applications if you take a black box approach and analyze the overall application performance of a computer system - you would not know whether that system had more CPUs with hard disks or less CPUs with more SSDs.

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's main SSD page.

For other SSD related terms see - flash SSD Jargon.

Most of this definition (above) by was first published in 2000.

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here are some more SSD articles

the future of enterprise data storage (circa 2020)
RAM SSDs versus Flash SSDs - which is Best?
principles of bad block management in flash SSDs
Flash Memory vs. Hard Disks - Which Will Win?
Can you tell me the best way to get to SSD Street?
How Bad is - Choosing the Wrong SSD Supplier?
Using SSDs to Boost Legacy RAID Performance
Hybrid Storage Drives - winners, losers and maybes
SSDs, tonic medicine and the next flash / flu pandemic
3 things that could have killed the flash SSD market
Flash vs DRAM Price Projections - for SSD Buyers
War of the Disks: Hard Disk Drives vs. Flash SSDs
Can you trust flash SSD performance benchmarks?
3 things that could have killed the flash SSD market
what will set the tone of the SSD market in 2012?
SSDs Pushing the Envelope in Blade Server Design
Z's Laws - Predicting Future Flash SSD Performance
Why Consumers Can Expect More Flaky Flash SSDs!
Clarifying SSD Pricing - where does all the money go?
Can you believe the word "reliability" in a 2.5" SSD ad?
if Fusion-io sells more does that mean Violin will sell less?
Fast Purge flash SSDs - when "Rugged SSDs" won't do the job
Calling for an End to Unrealistic SSD vs HDD IOPS Comparisons
the Case for Fast Boot SSDs (100mS or less) inside Petabyte SSD Backup Arrays
will the enterprise SSD market be big enough for all these companies [list] to grow?
Beware the distorting lens of viewpoint
as in - "SSDs are similar to..."
Can you trust SSD market data?
SSD ad - click for more info
"SSDs are a bit obsessive about how they organize their valid data. They prefer to have it neatly stacked together. Unfortunately, everyday use makes this type of neatness difficult, because the OS is constantly writing and deleting data of various sizes, leaving data strewn haphazardly throughout the SSD."
From the article Understanding SSDs (March 2014) - by Samsung - which is a good introductory blend of simple SSD design ideas and jargon aimed at SSD consumers.
"Recently we've been hearing more details about the implementation plans for a new type of fast enterprise SSD - memory channel storage - aka ultra low latency SSDs."
ULL SSDs - PCIe SSD killers or collabrative co-workers?
SSD ad - click for more info
"Solid State Drives" is too limiting a term for the market segment. Emulating a spinning disk is a not a great aspiration for solid state technologies, which are radically higher performing. Then again, car engines are still measured in horse power!
Morgan Littlewood, VP Marketing and Business Development at Violin Memory (August 2007) - in the article:- RAM SSDs versus Flash SSDs - which is Best? - War for the datacenter core

SSD news
SSD videos
SSD education
SSD Bookmarks
the Fastest SSDs
the SSD Heresies
Who's who in SSD?
the SSD Buyers Guide
SSD Jargon Explained
SSD Reliability Papers
Tuning SANs with SSDs
After SSDs... What Next?
Flash SSDs / RAM SSDs
the Top 20 SSD Companies
this way to the petabyte SSD
Introducing the 1" SSD Market
SSDs - the big market picture
Imprinting the brain of the SSD
Increasing Flash SSD Reliability
Storage Market Outlook to 2015
sugaring MLC for the enterprise
Hard way ahead for hard drives?
Surviving SSD sudden power loss
animal brands in the SSD market
Why I Tire of "Tier Zero Storage"
Data Recovery from Flash SSDs?
RAM Cache Ratios in flash SSDs
Big versus small - SSD architecture
What's the best / cheapest PC SSD?
Is the SSD Market Recession-Proof?
Branding Strategies in the SSD Market
3 Easy Ways to Enter the SSD Market
Encryption - impacts in notebook SSDs
Overview of the Notebook SSD Market
35 Years of SSDs - SSD Market History
a new way of looking at Enterprise SSDs
flash SSD capacity - the iceberg syndrome
Power, Speed and Strength in SSD brands
the Problem with Write IOPS - in flash SSDs
SSD Myths and Legends - "write endurance"
Data Integrity Challenges in flash SSD Design
why the notebook SSD crystal ball is still murky
Market Trends in the Rackmount SSD Market
an introduction to SSD Data Recovery Concepts
The single big idea about SSD acceleration is that it can give you the same performance increase as doubling or trebling your processor clock speed! In datacenters that means faster applications and budget saving by deploying less enterprise servers. In notebooks it means better performance and longer unplugged.. ...SSD Market Adoption model