Solid State Drive Buyer's Guide

MLC Makeover

After all of that talking up, we’ll risk being anticlimactic and say that the days of SLC could be numbered. Even Intel, the current leader in SSD sales, has backed off from its SLC-based drive messaging in recent months, perhaps in an effort to appease recession-strapped businesses. We’re hearing more about MLC in the enterprise these days. Some of it may have to do with price, but some of it is because MLC has made some significant improvements.

 

We mentioned earlier that SSD drives, and MLC models in particular, tended to lose their luster on write operations. This is largely because of the odd there-and-back process SSDs use when writing. Even if you only want to write a small amount of data to an SSD, say 8KB, the system has to send a 128KB stack of data to system memory. Of that 128KB, 8KB gets replaced with the desired data, then the whole 128KB wad gets sent back to the SSD. (Additionally, whereas read operations can simply assess the value of a cell in a single operation, writes to cells that have already been written once require an erasure of the cell before writing in the new data–two steps instead of one.) The difference between 8KB and 128KB is known as write amplification. All of that extra data being moved about takes more time.

Recently, though, SSD manufacturers have started updating their drive firmware with new algorithms that markedly reduce the size of the data block being sent to and from system memory. The effect on drive performance isn’t night and day different, but it helps.

Another recent enhancement is the TRIM command. TRIM solves the problem of SSDs getting progressively slower as blocks get written to. There’s an inherent mismatch in the way that operating systems and SSD controllers have tracked how and when data gets deleted. Resolving this mismatch usually happens in the drive’s cache, but it takes a lot of extra time. The TRIM command resolves certain elements of this mismatch and improves overall performance.

The catch is that the TRIM command must be supported by both the drive controller and the operating system. Windows 7 and Linux 2.6.28 both support it, as do an increasing number of controllers. Some SSD drives are firmware-upgradeable to support TRIM, some aren’t. Definitely check on this point before committing to a purchase and, after you purchase, refer back to the vendor’s support pages periodically for firmware updates. TRIM is still a recent advance, complete with plenty of speed bumps during early deployment, and will be prone to fine-tuning.

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  • Shadow703793
    Imo, I'd keep away with any SSD drive using a JMicron. Dosen't matter if the stutering,etc issues were fixed. Indylinx and Intel controllers are the best right now.

    Anyways, I got an X25-M G2 (OEM) for $220 @Newegg during Black Friday.
  • grimjester
    The point about getting a small SSD for software and a larger disk for data can't be stressed enough. The price per GB looks completely different if you only need 64G. There's little difference in price between the cheapest hard drive you can get and the cheapest 500G one.

    An SSD is just an extra cost of $150-300. It has no practical effect on the storage space your computer has.
  • nonxcarbonx
    This is an even better ssd article than anandtech's ssd anthology. Nice work.
  • Eggrenade
    I wouldn't say it's better than Anandtech's; there's no mention of random reads or writes, which is why performance just after startup is so good. It's also a lot less technical, which is probably better for most Tom's Guide readers.
  • Tomsguiderachel
    EggrenadeI wouldn't say it's better than Anandtech's; there's no mention of random reads or writes, which is why performance just after startup is so good. It's also a lot less technical, which is probably better for most Tom's Guide readers.

    Exactly :)
  • Tomsguiderachel
    nonxcarbonxThis is an even better ssd article than anandtech's ssd anthology. Nice work.

    Thank you. I hope it was a good fit for Tom's Guide readers' needs.
  • Anonymous
    Next page broken http://www.tomsguide.com/us/ssd-value-performance,review-1455-11.html, sorry couldnt find anywhere to submit feedback. Page not working on firefox 3.5.5 (does not scroll).
  • Tomsguiderachel
    none007Next page broken http://www.tomsguide.com/us/ssd-va [...] 55-11.html, sorry couldnt find anywhere to submit feedback. Page not working on firefox 3.5.5 (does not scroll).

    I'm using the same browser and that page works for me. I will report the bug, thanks.
  • Tomsguiderachel
    TomsguiderachelI'm using the same browser and that page works for me. I will report the bug, thanks.

    Oh--I see that you mean the final page of the article not the penultimate page. FYI There is no content on that last page so you didn't miss part of the article.
  • tommysch
    I think Ill stick to my 4x1TB RAID 0 array for now. BTW they are ghosted each week. o_0
  • nebun
    love my 4x ssd raid 0 500MB+ read and 300MB+ write
  • Luscious
    Another wonderful Swiss-cheese article from TG!

    Your author fails to mention in his "pros-and-cons" anything about the importance of the file system when choosing an SSD. It is a known issue with Windows XP that formatting a solid state drive as NTFS can cause the hard drive to randomly lock up. Netbook owners looking to replace their drives need to keep this in mind, especially on systems running XP.

    This is the same guy who wrote an article about ergonomics yet failed to mention anything about trackballs in his work.

    Thumbs down for you Tom's!
  • extremepcs
    "For comparison, we might look at a middle-of-the-roach HDD"

    :)
  • Shadow703793
    LusciousAnother wonderful Swiss-cheese article from TG!Your author fails to mention in his "pros-and-cons" anything about the importance of the file system when choosing an SSD. It is a known issue with Windows XP that formatting a solid state drive as NTFS can cause the hard drive to randomly lock up. Netbook owners looking to replace their drives need to keep this in mind, especially on systems running XP.This is the same guy who wrote an article about ergonomics yet failed to mention anything about trackballs in his work.Thumbs down for you Tom's!

    You do bring up a good point. What I would like to see are benchmarks for the different file systems available (ie FAT,NTFS, ext3,etc)
  • Tomsguiderachel
    Shadow703793You do bring up a good point. What I would like to see are benchmarks for the different file systems available (ie FAT,NTFS, ext3,etc)

    That sounds like a great article idea for Tom's Hardware!
  • JackNaylorPE
    Nothing to say against SSD performance but the exaggerated yearly time savings just don't take into account a little thing called reality. For example, how does Joe office worker get thru his day ?

    1.a Arrives at desk, hits PC on button and times how long it takes to boot into Windoze ?

    1.b Arrives at desk, hits PC on button grabs coffee cup and heads over to coffee machine ?

    2.a Needing to edit a Word proc document, opens word processor and stares at screen waiting for program to load ?

    2.2 Needing to edit a Word proc document, opens word processor and while program loads, scans over the boss's red pencil marks edits to get a handle on what he's gotta correct ?

    SSD technology is great and increased adoption will continue to drive down costs but these ROI arguments about increased productivity are not reflective of how humans (not robots) work.
  • pps
    I don't get it. This article first discribes how SLC is superior in every technical category, then it says that they are making improvements to MLC and concludes that MLC is the future.
    ???
  • williamvw
    nonxcarbonxThis is an even better ssd article than anandtech's ssd anthology. Nice work.

    Thanks! However, even I'll second Eggrendade's comment. I wrote this piece specifically as an introduction to SSDs for those still getting their feet wet -- not the type wanting an in-depth analysis of file system performance. Anand's series is excellent but obviously far more technical. Different strokes.
  • williamvw
    ppsI don't get it. This article first discribes how SLC is superior in every technical category, then it says that they are making improvements to MLC and concludes that MLC is the future. ???

    It's a price vs. performance issue. Yes, SLC rules on performance, but its progress has stayed fairly flat while MLC continues to improve while driving down cost per gig. Thus while SLC remains the technical champion on benchmarks, MLC has caught up enough to make it more attractive on a price/performance basis in an increasing number of environments.