different types of SSD flash memory

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Data StorageThere are different types of SSD Flash memory in data storage and networking world. And both types are most frequently used in different sector in different domains. But after comparison you can find NAND flash memory is widely used flash memory. The reason why NAND flash being used widely is mentioned at later section of this post, so requesting you read from beginning to understand well.

All your cell phones or portable devices contains SSD with NOR flash memory. Why so? this is mentioned in later section of this post.

If you do not know about basic of SSD Flash Memory you can visit our another post : Know about your SSD (Solid State Drive) Memory

For in-depth understanding, you can read one of the famous book in the field of data storage and networking is Data Storage and networking by Nigel Poulton

1. Anatomy of Flash Memory

dstn-ssd-anatomy

In SSD flash memory , there three things: cell, page, and block, which are the basic building block of block (storage unit).

  1. Cell: Flash memory is made up of flash cell
  2. Page: cells are grouped into pages (4K, 8K, 16K etc)
  3. Block: Pages are grouped into blocks (128 K, 256 K, 512 K)

Erase cycle or you can say reset of data on block level , neither at page level nor at cell level. Erase cycle on block level and which is finite i.e. 1,00,000 ( one Lac ) in NAND flash.

You must have observed that, when you laptop is new on that time write is very faster. In first cycle write in SSD drive is very fast and then slow due to Erase cycle.

2. Types of Flash Memory

There are two different types of flash memory.

  • NAND Flash ( most widely used)
  • NOR Flash memory

3. Key Points of NAND Flash Memory

NAND flash memory is most widely used flash memory in the world.

  • small cell: Design with small cell
  • Low cost: it has low cost per bit for storage data
  • PE Cycle: PE (Programm Erase) cycle is 1,00,000 ( one lac)
  • Used as high density medium for consumer devices.
  • most widely used: NAND is most widely used flash memory because few reason: consumes lesser amount of space on disk means more density, low cost per bit storage.
  • Write: faster on write compared to NOR
  • Read: slower on read compared to NOR
  • Read: slower on read compared to NOR
  • Power consumption: NAND consumes more power compared to NOR flash drive.

4. Key Points of NOR Flash Memory

  • for Portable device: is typically used for storing code and direct execution in portable electronic devices
  • For Write : Nor is typically slow on write and consume more power than NAND
  • For read: NOR is fast on read and consumes less power.
  • Power consumption: NOR consumes less power.

5. Types of NAND Flash Memory

  • SLC (Single Level Cell): can store one bit of data, highest performance, lowest density and expesive
  • MLC (Mulit Level Cell) : store two bit of data per cell by applying different cell voltage. Lower PE cycle 10,000 ( less than 10 x). read about eMLC
  • Triple cell:

6. Power consumption of different drive

Power consumption of different drive of device

Device NameApproximate Power consumption
DRAM DIMM module (1GB)5W
HDD with 15000 RPM drive17.2 W
HDD - 7200 RPM drive (750GB) 12.5W
SSD High performance flash (128 GB)2W

If you carefully observed this table you can find power consumption in SSD flash memory is less compared with DRAM, HDD. Dynamic RAM (DRAM) is much cheaper as compared to static RAM.

In Static RAM 4-5 transistor required to store data whereas in dynamic RAM only single transistor required to store data. Due to cost DRAM is more widely used and cost effective.

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