There are 2 different types of SSD Flash memory NAND Flash memory and NOR flash memory in data storage and networking world.
1. Overview of SSD Flash memory types
And both types of SSD flash memory: NAND flash memory and NOR flash memory are most frequently used in different sectors in different domains. But after comparison, you can find NAND flash memory is a widely used flash memory. The reason why NAND flash being used widely is mentioned in a later section of this post, so requesting you read from the beginning to end to understand well.
All your mobile phones or portable devices contain SSD with NOR flash memory. Why so? this is mentioned in a later section of this post.
If you do not know about basic of SSD Flash Memory you can visit 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
2. Anatomy of Flash Memory
In SSD flash memory , there three things: cell, page, and block, these are the basic building block of block (storage unit).
- Cell: Flash memory is made up of flash cell
- Page: cells are grouped into pages (4K, 8K, 16K etc)
- Block: Pages are grouped into blocks (128 K, 256 K, 512 K)
Erase cycle or reset of data will be done on block level, neither at page level nor at cell level. Erase cycle on block level and which is finite number of times i.e. 1,00,000 ( one Lac ) in NAND flash.
You must have observed that, when you laptop is new on that point in time write operation is very faster. In first cycle write in SSD drive is very fast and then slowly and gradually it become slow due to Erase cycle.
3. Types of SSD Flash Memory
There are two different types of SSD flash memory.
- NAND Flash ( most widely used)
- NOR Flash memory
4. 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.
5. 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.
6. 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:
7. Power consumption of different drive
Power consumption of different drive of device
|Device Name||Approximate Power consumption|
|DRAM DIMM module (1GB)||5W|
|HDD with 15000 RPM drive||17.2 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 transistors required to store data whereas in dynamic RAM only a single transistor required to store data. Due to cost DRAM is more widely used and cost-effective.
Wiki – IBM RAMAC 350 Hard Disk
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