The SSD Relapse: Understanding and Choosing the Best SSD
by Anand Lal Shimpi on August 30, 2009 12:00 AM EST- Posted in
- Storage
One Tough Act to Follow
What have I gotten myself into? The SSD Anthology I wrote back in March was read over 2 million times. Microsoft linked it, Wikipedia linked it, my esteemed colleagues in the press linked it, Linus freakin Torvalds linked it.
The Anthology took me six months to piece together; I wrote and re-wrote parts of that article more times than I'd care to admit. And today I'm charged with the task of producing its successor. I can't do it.
The article that started all of this was the Intel X25-M review. Intel gave me gold with that drive; the article wrote itself, the X25-M was awesome, everything else in the market was crap.
Intel's X25-M SSDs: The drives that started a revolution
The Anthology all began with a spark: the SSD performance degradation issue. It took a while to put together, but the concept and the article were handed to me on a silver platter: just use an SSD for a while and you’ll spot the issue. I just had to do the testing and writing.
OCZ's Vertex: The first Indilinx drive I reviewed, the drive that gave us hope there might be another.
But today, as I write this, the words just aren't coming to me. The material is all there, but it just seems so mature and at the same time, so clouded and so done. We've found the undiscovered country, we've left no stone unturned, everyone knows how these things work - now SSD reviews join the rest as a bunch of graphs and analysis, hopefully with witty commentary in between.
It's a daunting, no, deflating task to write what I view as the third part in this trilogy of articles. JMicron is all but gone from the market for now, Indilinx came and improved (a lot) and TRIM is nearly upon us. Plus, we all know how trilogies turn out. Here's hoping that this one doesn't have Ewoks in it.
What Goes Around, Comes Around
No we're not going back to the stuttering crap that shipped for months before Intel released their X25-M last year, but we are going back in the way we have to look at SSD performance.
In my X25-M review the focus was on why the mainstream drives at the time stuttered and why the X25-M didn't. Performance degradation over time didn't matter because all of the SSDs on the market were slow out of the box; and as I later showed, the pre-Intel MLC SSDs didn’t perform worse over time, they sucked all of the time.
Samsung and Indilinx emerged with high performance, non-stuttering alternatives, and then we once again had to thin the herd. Simply not stuttering wasn't enough, a good SSD had to maintain a reasonable amount of performance over the life of the drive.
The falling performance was actually a side effect of the way NAND flash works. You write in pages (4KB) but you can only erase in blocks (128 pages or 512KB); thus SSDs don't erase data when you delete it, only when they run out of space to write internally. When that time comes, you run into a nasty situation called the read-modify-write. Here, even to just write 4KB, the controller must read an entire block (512KB), update the single page, and write the entire block back out. Instead of writing 4KB, the controller has to actually write 512KB - a much slower operation.
I simulated this worst case scenario performance by writing to every single page on the SSDs I tested before running any tests. The performance degradation ranged from negligible to significant:
| PCMark Vantage HDD Score | New | "Used" |
| Corsair P256 (Samsung MLC) | 26607 | 18786 |
| OCZ Vertex Turbo (Indilinx MLC) | 26157 | 25035 |
So that's how I approached today's article. Filling the latest generations of Indilinx, Intel and Samsung drives before testing them. But, my friends, things have changed.
The table below shows the performance of the same drives showcased above, but after running the TRIM instruction (or a close equivalent) against their contents:
| PCMark Vantage HDD Score | New | "Used" | After TRIM/Idle GC | % of New Perf |
| Corsair P256 (Samsung MLC) | 26607 | 18786 | 24317 | 91% |
| OCZ Vertex Turbo (Indilinx MLC) | 26157 | 25035 | 26038 | 99.5% |
Oh boy. I need a new way to test.
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GourdFreeMan - Tuesday, September 1, 2009 - link
You would, in fact, be incorrect. I refer you to ANSI/IEEE Std 1084-1986, which defines kilo, mega, etc. as powers of two when used to refer to sizes of computer storage. It was common practice to use such definitons in Computer Science from the 1970s until standards were changed in 1991. As many people reading Anandtech received their formal education during this time period, it is understandable that the usage is still commonplace.Undersea - Monday, August 31, 2009 - link
Where was this article two weeks ago before I bought my OCZ summit? I hope this little article will jump start samsung.Thanks for all the hard work :)
FrancoisD - Monday, August 31, 2009 - link
Hi Anand,Great article, as always. I've been following your site since the beginning and it's still the best one out there today!
I mainly use Mac's these days and was wondering if you knew anything about Apple's plans for TRIM??
Thanks for all the fantastic work, very technical yet easy to understand.
François
Anand Lal Shimpi - Monday, August 31, 2009 - link
Thanks for your support over the years :)No word on Apple's plans for TRIM yet, I am digging though...
Take care,
Anand
Dynotaku - Monday, August 31, 2009 - link
Amazing article as always, now I just need one that shows me how to install just Win 7 and my Steam folder to the SSD and move Program Files and "My Documents" or whatever it's called in Win7 to a mechanical disk.GullLars - Monday, August 31, 2009 - link
A really great article with loads of data.I only have one complaint. The 4kb random read/write tests in IOmeter was done with QD=3, this simulates a really light workload, and does not allow the controllers to make use of the potential of all their flash channels. I've seen intels x25-M scale up to 130-140 MB/s of 4KB random read @ QD=64 (medium load) with AHCI activated. I have not yet tested my Vertex SSDs or Mtron Pro's, but i suspect they also scale well beyond QD=3.
It would also be usefull to compare the different tests in the HDDsuite in PCmark vantage instead of only the total score.
Anand Lal Shimpi - Monday, August 31, 2009 - link
The reason I chose a queue depth of 3 is because that's, on average, what I found when I tried heavily (but realistically) loading some Windows desktop machines. I rarely found a queue depth over 5. The super high QDs are great for enterprise workloads but I don't believe they do a good job at showcasing single user desktop/notebook performance.I agree about the individual HDD suite tests, I was just trying to cut down on the number of graphs everyone had to mow through :)
Take care,
Anand
heulenwolf - Monday, August 31, 2009 - link
Anand,I'd like to add my thanks to the many in the comments. Your articles really do stand out in their completeness and clarity. Well done.
I'm hoping you or someone else in the forums can shed some light on a problem I'm having. I got talked into getting a Dell "Ultraperformance" SSD for my new work system last year. Its a Samsung-branded SLC SSD 64 GB capacity. As your results predict, its really snappy when its first loaded and performance degrades after a few months with the drive ~3/4 full. One thing I haven't seen predicted, though, is that the drives have only lasted 6 months. The first system I received was so unstable without explanation that we convinced Dell to replace the entire machine. Since then, I'm now on my second SSD refurb replacement under warranty. In both SDD failures, the drive worked normally for ~6 months, then performance dropped to 5-10 MB/sec, Vista boot times went up to ~15 minutes, and I paid dearly in time for every single click and keypress. Once everything finally loaded, the system behaved almost normally. Dell's own diagnostics pointed to bad drives, yet, in each case, the bad SSD continued to work just at super slow speeds. I was careful to disable Vista's automatic defrag with every install.
My IT staff has blamestormed first Vista (we're still mostly an XP shop) and now SSDs in general as the culprit. They want me to turn in the SSD and replace it with a magnetic hard drive. So, my question is how to explain this:
A) Am I that 1 in a bazillion case of having gotten a bad system followed by a bad drive followed by another bad drive
B) Is there something about Vista - beyond auto defrag - that accelerates the wear and tear on these drives
C) Is there something about Samsung's early SSD controllers that drops them to a lower speed under certain conditions (e.g. poorly implemented SMART diagnostics)
D) Is my IT department right and all SSDs are evil ;)?
Ardax - Monday, August 31, 2009 - link
Well, first you could point them to this article to point out how bad the Samsung SSDs are. Replace it with an Intel or Indilinx-based drive and you should be fine. Anecdotes so far indicate that people have been beating on them for months.As far as configuring Vista for SSD usage, MS posted in the Engineering Windows 7 Blog about what they're doing for SSDs. [url=http://blogs.msdn.com/e7/archive/2009/05/05/suppor...">http://blogs.msdn.com/e7/archive/2009/0...nd-q-a-f...]Article Link[/url].
The short version of it is this: Disable Defrag, SuperFetch, ReadyBoost, and Application and Boot Prefetching. All these technologies were created to work around the low random read/write performance of traditional HDs and are unnecessary (or unhealthy, in the case of defrag) with SSDs.
heulenwolf - Monday, August 31, 2009 - link
Thanks for the reply, Ardax. Unfortunately, the choice of SSD brand was Dell's. As Anand points out, OEM sales is where Samsung's seems to have a corner on the market. The choices are: Samsung "Ultraperformance" SSD, Samsung not-so-ultraperformance SSD, Magnetic HDD, or void the warranty by getting installing a non-Dell part. I could ask that we buy a non-Dell SSD but since installing it would preclude further warranty support from Dell and all SSDs have become the scapegoat, I doubt my request would be accepted. Additionally, the article doesn't say much about drive reliability which is the fundamental problem in my case.I'll look into the linked recommendations on Win 7 and SSDs. I had already done some research on these features and found the general concensus to be that leaving any of them enabled (with the exception of defrag) should do no harm.