Is a MLC still slower and less reliable than a SLC SSD?

Question

Most laptop vendors seem to supply relatively cheap MLC drives with their pre-built configurations.

I know that the traditional drill is that a SLC is fast and reliable while a MLC is slower and less reliable; but I've heard that in a last years lots of elaborate algorithms and workarounds made MLC almost as good as SLC. Can anyone show me some definitive modern benchmarks that either prove or dismiss this fact?

Answer 1

All recent consumer drives use MLC flash. Even some enterprise-focused SSDs also use MLC, although with Intel's MLC-HET:

Similar to frequency binning CPUs, the highest quality NAND with the tightest margins gets binned into MLC-HET while everything else is shipped as standard MLC. And just like with frequency binning, there's a good chance you'll get standard MLC that will last a lot longer than it's supposed to. In fact, I've often heard from manufacturers that hitting up to 30K p/e cycles on standard MLC NAND isn't unrealistic. With its MLC-HET Intel also more frequently/thoroughly refreshes idle NAND cells to ensure data integrity over periods of extended use.

So the extra P/E cycles - and therefore increased longevity of the flash memory - come from picking the highest quality NAND chips, as well as adding a significant spare area of 41%.

As for performance, the MLC Intel 710 is generally slightly slower than its older SLC cousin, the X25-E (but the 710 is far cheaper to compensate). Regardless, SandForce MLC drives usually dominate SSD benchmarks due to real-time compression in the controller, rather than depending upon the intrinsic speed of SLC.

Answer 2

You will want to look at a few other qualities of an SSD in order to make your purchase decision.

1. Does the SSD support TRIM? As the SSD gets filled, it will need to write where data once existed. However, the nature of the SSD is that it must first delete the information from the actual space before it writes new data. This means that as your SSD gets to be used for a while and fills up, it will become slower. TRIM is a functionality of the SSD that will allow the files to be deleted and the space cleaned up as it occurs.

2. IOPS - You will find several SSDs that are within the same price range as well as the amount of space. However, you will need to look at the actual speeds of the read/writes to make your decision as there are so many variances between the drives. AnAndTech (http://www.anandtech.com/bench/SSD/65) has an excellent chart for comparing the different speeds and other comparisons of the SSDs.

3. RAID - Keep in mind that you will want to just do one SSD drive and skip the whole idea of RAID. Even though this is very possible to do and you do get the performance gain as expected, you lose the functionality of TRIM. Over time it will slow down.

4. Z68 SSD Caching. Does your new laptop support SRT? SRT is the ability of taking a 20GB to 64GB SSD Drive and use it for caching your hard drive. You will get the perks of lots of space and the speed of the SSD. Your most frequently used files will be stored on the SSD for recall (most common applications, game files, OS startup files). This is my current configuration and I love it. It's truly amazing.

5. Sata2/Sata3 - Make sure that you purchase the correct SSD interface for your laptop. If your laptop supports Sata3 then make sure you get a Sata3 SSD Drive. Sata2 is capped at ~300MBps where as Sata3 is capped at ~600MBps. You will be wasting money/performance on purchasing a Sata2 SSD on a Sata3 laptop.