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A solid-state drive (SSD) is a data storage device that uses solid-state memory to store persistent data.
Difference: Flash Drive
Emulates a hard disk drive interface
Could be easily replaced in most applications
History
Era of vacuum tube computers In the 1970s and 1980s, IBM, early
supercomputers In 1978, StorageTek, first modern type of SSD In the mid-1980s, an array of 1 megabit DIP
RAM Chips and a custom controller card In 1995, M-Systems, Flash-based SSD, military
and aerospace industries
Flash based
More rugged and compact for the consumer market
Do not require batteries Significantly slower than DRAM, but
perform better than traditional hard drives 250 MB/s effective read/write
DRAM based
Ultra fast data access Incorporate internal battery and backup
storage systems Hibernate: RAM and the back-up storage Especially useful on computers that
already have the maximum amount of supported RAM
Advantages for RAM & Flash
Faster start-up Fast random access for reading Faster boot and application launch times No noise High mechanical reliability Relatively deterministic read performance Lower weight and size Failures occur either 'on write' or 'on erase'
Advantages for Flash
low power consumption and heat production when in active use
Ability to endure extreme shock, high altitude, vibration and extremes of temperature
Disadvantages
Price40GB HDD, Oct 2005, 400 CNY640GB HDD, Oct 2008, 560 CNY32GB SSD, Oct 2008, 1000 CNYRAM:Flash:HDD = 35:20:1
Disadvantages
Capacity Vulnerability Limited write (erase) cycles Slower write speeds Lower storage density Higher power consumption
Applications
Run lightweight operating systems designed specifically
Hybrid drive By Oct 2009, 54%
notebooks
Hybrid Disk
A hybrid disk uses a small SSD as a buffer for a larger drive
All dirty blocks can be flushed to the actual hard drive based on:TimeThresholdLoss of power/computer shutdown
Commercialization
Asus Eee PC subnotebook, Oct 2007 “One Laptop Per Child” project, Dec 2007 Apple MacBook Air, Jan 2008 Lenovo ThinkPad X300, Feb 2008 sales increase by 70% per year,
2007~2012, International Data Corp.