Difference betten SLC, MLC and TLC NAND SSD

Difference betten SLC, MLC and TLC NAND SSD

Postby curious » Thu Feb 23, 2012 11:39 pm


What is the difference between the SLC, MLC and TLC NAND SSDs ? As a consumer what do I need to know about it ?
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Postby hubert » Thu Feb 23, 2012 11:43 pm

Let us first talk about the difference between the SLC and the MLC. Basically and SLC is nothing but an ON / OFF switch. You apply a voltage to a cell and keep increasin it till it reaches the ON state. The cell has two states - the ON state and the OFF state.

The MLC has two bits per cell. Instead of two voltage states we have four states (00, 01, 10, 11).


The TLC makes the density three times the SLC by using three bits per cell, or eight voltage states (000, 001, 010, 011, 100, 101, 110, and 111).
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Postby hubert » Fri Feb 24, 2012 12:08 am

The TLC nands offer triple the density in the same die size as the SLC. So it is able to make it cheaper. However, the TLCs may be less reliable than its SLC and MLC counterpart.

Also the price advantage between the TLC and the MLC is not as dramatic as between the SLC and the MLC. The MLC roughly costs half to produce than the SLC. But TLC is only 30% less in cost of production than the MLC.

The migration from SLC to MLC is more cost effective than the migration from MLC to TLC. But the technology is maturing fast and 2 years down the line we may have more cost effective NAND SSDs.

At present the cost of the SSDs are as follows

64 GB = $100
128 GB = $200
256 GB = $400

In my view the best thing to do is to buy 64 GB SSD. It may take couple of year to fill the Hard Disk ( assuming you do not do a hell lot of video, and if you do - buy and external USB 3.0 drive). After two years buy the 256 GB SSD - will cost about the same as the 64 GB SSD now.
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Postby hubert » Fri Feb 24, 2012 12:17 am

The read and the write time for the TLC is slower. You get higher storage but have to sacrifice the speed a bit.
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Re:

Postby ihaveaquestion » Mon Jul 09, 2012 1:25 am

For regular consumers you do not need all the storage with NAND SSD. All you need is about 32 GB or maybe 64 GB of SSD and a larger regurar 1 TB of hard drive. You get the best of both world - a fast cached drive and large capacity drive when you need more storage ( but at lower speed).
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Re:

Postby vishu » Mon Aug 20, 2012 10:42 pm

ihaveaquestion wrote:For regular consumers you do not need all the storage with NAND SSD. All you need is about 32 GB or maybe 64 GB of SSD and a larger regurar 1 TB of hard drive. You get the best of both world - a fast cached drive and large capacity drive when you need more storage ( but at lower speed).

I agree with this. Unfotunately, companies are promoting SSD as if they are the real game changers. On the top of it, the UltraBooks, Sleek Books and Macbook Air requires that the SSD be part of it. By judiciously choosing a regular form factor ( aka normal thickness) laptop and sprinkling it with a little bit of SSD should be good to go. Wait for Windows 8 for a fast boot. Yes you can remove metro in Windows 8, if you hate it.
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