CF2 03 - Extra SSD.pdf

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SSD
(Solid State Disk)
http://en.wikipedia.org/wiki/Solid-state_drive
SSD (Solid State Disk) drives
• Most SSD drives gives very good performance 4x ~ 100x
– No noise, low weight, power and heat generation
– Extremely low seek times and good resistance to shock
• SSD revolution (2008?)..., now evolution
– Still expensive but will probably own a lot of the market in the next
years to come
• Many different brands (> 50)
– Intel, Samsung,OCZ, Corsair, Kingston...
• Especially well suited for laptops
and RAID 0 since it scales well
– Power consumption
– Less wear and tear on cells
• A big step in the computer history!
http://en.wikipedia.org/wiki/Category:Solid-
state_computer_storage_media
SSD (2009)
performance
laptop
SSD, Intel G2 – SATA 2
USB-disk
HD
How SSD work I
http://en.wikipedia.org/wiki/Flash_memory
• The building block of NAND flash is the N-channel
MOSFET transistor cell
• Voltage levels
– 2, 4 and 8 levels of voltage
• SLC (Single-Level Cell)
– Holds 1 bit of data
• MLC (Multi-Level Cell)
–
Holds 2 bits of data
• TLC (Triple-Level Cell)
–
Holds 3 bits of data
When you program a cell, you are placing
a voltage on the control gate, while source
and drain regions are held at 0V.
The voltage forms an electric field, which
allows electrons to tunnel through the
silicon oxide barrier from the N-channel to
the floating gate.
The silicon oxide acts as an insulator and will not
allow electrons to enter or escape the floating gate
unless an electrical field is formed.
To erase a cell, you apply voltage on the silicon
substrate (P-well in the picture) and keep control gate
voltage at zero.
An electric field will be formed which allows the
electrons to get through the silicon oxide barrier.
Understanding SLC/MLC/TLC NAND
http://www.anandtech.com/show/5067/understanding-tlc-nand
Bits per cell
Price
Degradation
Performance

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