OCZ Vertex 120 GB SSD review

This is an excerpt from a full review by guru3d of the OCZ Vertex 120GB SSD.  If you have been wondering about the durability of these new solid state drives, you will either be pleasantly surprised, or not so convinced that this is the new “holy grail” of storage.

The difference between SLC and MLC

All flash memory is not created equal. There are 2 main types, SLC and MLC:
SLC and MLC (single and multi level cells) SLC stores one bit per cell, MLC doubles it. MLC -we see a lot in flash-memories used for example in your digital camera. If we break it down:

• SLC is faster, and has around 10,000 up-to 1 million write cycles
• MLC is somewhat slower but cheaper, unfortunately also less reliable (sometimes as few as 10,000 write cycles).

And that’s where we land at limited write cycles. The reality is that you purchase a SSD drive on borrowed time. By its very nature, flash memory cells can resist only so many write cycles before they are prone to failure.

Typically SLC flash storage will wear out after hundreds of thousands of write cycles, while high endurance flash storage is often marketed with an endurance of 1-5 million write cycles.

Special file systems or firmware designs mitigate this problem by spreading writes over the entire device (so-called wear leveling), rather than rewriting files in oneplace. Wear leveling is designed to prevent rewriting the same cell constantly. Pretty much: data is constantly spread out over the entire drive so that all cells will be written equally over time. Wear leveling isn’t done in hardware, it is done in firmware on the SSD. It will spread the writes over the whole range of the NAND storage, so you can’t really wear out one area while the rest stayed untouched.

At this very moment the life-span of a typicalSSD drive MTBF (Mean Time Before Failure) is 1,500,000 to 2,000,000 hours, and honestly… that number means just nothing. Fact is, we just do not know how long a drive will last or how long it’ll take before it wears out.

The limited write cycles is per cell, not per disk, and all controllers have hadwear leveling (using different cells) for a few years now. Any “bad” cell will be mapped out just like a bad block on a hard drive (transparently).

MLC lifespan then, how long will it really last? Well, only thefuture will tell… However, with modern flash technology and error correction, the reliability of the drive in a PC could exceed 10 years with normal usage. This remains a gamble though. Most manufacturers will therefore grant a two year warranty. We would very much like to see a 5 year warranty from manufacturers, there’s nothing worse than data-loss. If the industry makes a commitment, we as consumerswould certainly feel more confident in purchasing an SSD.

For the complete review, hit the source link below.

source:guru3d