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I have a Kingston mSATA SSD (Kingston SSDNow mS100 64GB mSATA Internal Solid State Drive SMS100S2/64G) I bought about 6 months ago. When I tested it with AS SSD Benchmark right after the first installation, the speed wear about 210 MS/s read and 120 MS/s write. Kingstons states 255 MB/s read and 170 MB/s writes so it checked out.

Over the last few days I started to feel the SSD is getting slow, so tested it again. I was very surprised I got 50 MB/s read and 13 MB/s write speed. It is a massive speed degradation, especially the read part.

Is this normal? I am suing Windows 8, the SSD and OS both support trim. I have about 15% free disk space.

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Is your Windows 8 installation optimized for SSD? If not, you might be writing to the SSD way too much and might end lowering the SSD life. –  Peter Feb 7 '13 at 11:59
    
@Peter I used SSD Tweaker from the start, so no indexing etc.. –  Igor Kulman Feb 7 '13 at 12:00
    
It would be a pain but if you could clone the drive, do a secure erase and then write back the clone you could test if the degradation was due to writes over time. –  Brad Patton Feb 7 '13 at 15:49

3 Answers 3

up vote 2 down vote accepted

Using an SSD to the point where it has 15% free space means that pretty much every block is fragmented. Even TRIM can't completely fix this, especially on a Sandforce drive (note: I couldn't find any data on the drive you're talking about, so I don't know if it's a Sandforce or other controller.)

Two things to make your performance better: First, try to keep more free space on the drive (inconvenient, I know). Second, once you have more space, clone your drive, secure erase it, and write the data back on so no blocks are fragmented (really inconvenient, I know. And it won't last long as a fix if you keep using the drive.) TRIM won't help all that much. The only real solution is to get a larger SSD or put your data on another drive.

tl;dr: It's a limitation of having such a small SSD; any SSD goes a ton slower when it lacks free space.

My SU answer about SSD free space

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Why would fragmentation slow down a SSD? There is no seek time or head that needs to readjust. In fact I was under the impression the controllers purposefully fragmented data for wear-leveling. –  Kyle Feb 7 '13 at 20:12
    
Good point in general, not so much with Sandforce. Since the Sandforce controller compresses all of it's data, fragmented data means it has to do more work to access it (or something. anandtech.com/show/6107 has some discussion on Sandforce TRIM.) I'm guessing this drive is SF internally because of the read speed issue and because Kingston uses a bunch of SF controllers. –  Marcus Chan Feb 7 '13 at 20:25
    
Thanks for the clarification. –  Kyle Feb 7 '13 at 20:36

A few things that spring to mind:

  1. Try to free up some space, performance goes down pretty rapidly when the drive is too full.
  2. Check for new versions of the driver, there might be a bug in the current one.
  3. Check the SMART stats of the drive, you can see here if there's anything very wrong with the drive. This part isn't easy though, the raw SMART numbers are very confusing. (this might help you.)
  4. 64GB drives are quite a bit slower than larger sized drives. This may (or may not, I really don't know) to cause the speed to go down much faster when the drive is nearly full. Which will happen pretty fast on a 64GB drive.
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1. got it to 20% free space and no difference, I will try to get more, 2. nothing is available, 3. SMART showing no problems –  Igor Kulman Feb 7 '13 at 12:27

I found this link, quoted in Wikipedia (en), about SSD: http://www.stec-inc.com/downloads/whitepapers/Benchmarking_Enterprise_SSDs.pdf

"SSD performance depends heavily on the workload"

"An empty SSD will run much faster than an SSD filled with data."

Can it be useful?

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