Scrambling Data to Improve Reliability?

I secure erase all SSDs before I run any test, unless I'm testing used performance. On a modern SSD, performing an ATA Secure Erase takes anywhere from 30 - 50 seconds in most cases. The first time I went to secure erase the SiliconEdge Blue it took almost 17 minutes. I asked Western Digital what was going on, and got an interesting explanation.

The smaller NAND flash gets, the more prone the cells are to developing bit errors. That's why SandForce made such a big deal out of its controllers making 34nm possible thanks to extra error correction and redundancy.


SandForce's controllers attempt to fix bit errors in order to enable the use of cheaper MLC NAND

Western Digital found that writing certain combinations of data were more prone to generating these bit errors on smaller dimension flash (< 50nm). To prevent these sorts of errors from cropping up, the controller reorganizes (or scrambles) the data it's fed before writing it to the flash. When you go back to read the data off the flash, it's unscrambled before sending it back to the host controller so you get the data you requested.

As a side effect, the controller can't simply perform a flash erase to zero out the contents of the drive. Instead the SiliconEdge Blue has to physically write (a F or 0) to every NAND flash cell on the drive itself, which takes some time. On the bright side, WD does this to improve data integrity (or more likely to use cheaper MLC NAND without sacrificing reliability). The only downside is that a secure erase, which you shouldn't need to do that often, will take a long time to complete.

The Controller Sequential Read/Write Speed
Comments Locked

64 Comments

View All Comments

  • Griswold - Thursday, March 4, 2010 - link

    No, numbnuts. He was just being careful because depending on what performance figure you look at, they're simply faster and in other cases thes dance circles around a spindle drive. A decent or good SSD is always much faster than common desktop HDDs. But not everyone cares about that.
  • DukeN - Wednesday, March 3, 2010 - link

    At this point the Intel reliability is greater IMHO as it has already gone through testing by hundreds of thousands of users, if not millions.

    And higher for mediocre performance is just not going to cut it. Maybe in six months when etailers are forced to sell them at 50% off to clear their inventory these will have an impact on pricing for most models.
  • mrsushi - Thursday, March 4, 2010 - link

    Would be interesting to know how many SSDs has Intel and co. sold.

    Kingston is not my favourite RAM maker, but their SSDs surely look a lot more solid than this WD. WD should wake up and put 5th gear in doing something more original.

    and about SSDs ... I would say that in less than 10 Years, RAM will be dead and buried. All PCs will work directly from SSDs. Its nearly there, start your OS directly where you left it yesterday when you went to bed...
  • semo - Wednesday, March 3, 2010 - link

    at 50% they still wouldn't be competing with other similar offerings. The MSRP needs to be halved before getting a clearance price... that would be a decent deal today but it won't happen today. So not much point to the consumer from these drives. Decent test bed for the lazy WD I guess
  • pullmyfoot - Wednesday, March 3, 2010 - link

    maybe not a million yet
  • semo - Wednesday, March 3, 2010 - link

    ... and does anyone know the release date for europe?
  • Conscript - Wednesday, March 3, 2010 - link

    when I first started reading this, I thought the 256GB was $529, and I was still contemplating if it was worth it over the 160GB Intel at $429.... then I came ot the end and see that that was the 128GB price and the 256GB is $999? No frakking way WD, good luck selling even one of these...
  • coolkev99 - Wednesday, March 3, 2010 - link

    Nice to see WD enter the SSD market. I'd take the plunge on this if they can get the price a bit lower. That's what needs to happen for these drive to truely go mainstream, and it's the only thing holding me back.
  • vol7ron - Wednesday, March 3, 2010 - link

    Why would it be the only thing holding you back? The Randoms on these drives are horrific. I'd rather wait for the new onset of SSDs that are going to put the Vertex2Pro and Intel G2s to shame.
  • coolkev99 - Thursday, March 4, 2010 - link

    Did you look at overall performace (PCMark Vantage) even with this "horrific" performace it's almost 50% faster than one of the fastest mechanical drives out there. I HATE hard drive slowness on my systems, chugging just load load an application. It's 2010 for gods sake and were still using more or less 1960's tech.

Log in

Don't have an account? Sign up now