Solid-State Drive

Ding Ruogu

Kong Liang

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

Difference: Hard Disk Drive

No moving parts No mechanical delays

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

Architecture and function

DRAM volatile memory NAND flash non-volatile memory

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

Comparison with hard disk drives

Advantages Disadvantages

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 RAM

Extremely low read latency times Extremely fast write

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.