The SSD Relapse: Understanding and Choosing the Best SSD
by Anand Lal Shimpi on August 30, 2009 12:00 AM EST- Posted in
- Storage
Intel's X25-M 34nm vs 50nm: Not as Straight Forward As You'd Think
It took me a while to understand exactly what Intel did with its latest drive, mostly because there are no docs publicly available on either the flash used in the drives or on the controller itself. Intel is always purposefully vague about important details, leaving everything up to clever phrasing of questions and guesswork with tests and numbers before you truly uncover what's going on. But after weeks with the drive, I think I've got it.
| X25-M Gen 1 | X25-M Gen 2 | |
| Flash Manufacturing Process | 50nm | 34nm |
| Flash Read Latency | 85 µs | 65 µs |
| Flash Write Latency | 115 µs | 85 µs |
| Random 4KB Reads | Up to 35K IOPS | Up to 35K IOPS |
| Random 4KB Writes | Up to 3.3K IOPS | Up to 6.6K IOPS (80GB) Up to 8.6K IOPS (160GB) |
| Sequential Read | Up to 250MB/s | Up to 250MB/s |
| Sequential Write | Up to 70MB/s | Up to 70MB/s |
| Halogen-free | No | Yes |
| Introductory Price | $345 (80GB) $600 - $700 (160GB) | $225 (80GB) $440 (160GB) |
The old X25-M G1
The new X25-M G2
Moving to 34nm flash let Intel drive the price of the X25-M to ultra competitive levels. It also gave Intel the opportunity to tune controller performance a bit. The architecture of the controller hasn't changed, but it is technically a different piece of silicon (that happens to be Halogen-free). What has changed is the firmware itself.
The old controller
The new controller
The new X25-M G2 has twice as much DRAM on-board as the previous drive. The old 160GB drive used a 16MB Samsung 166MHz SDRAM (CAS3):
Goodbye Samsung
The new 160GB G2 drive uses a 32MB Micron 133MHz SDRAM (CAS3):
Hello Micron
More memory means that the drive can track more data and do a better job of keeping itself defragmented and well organized. We see this reflected in the "used" 4KB random write performance, which is around 50% higher than the previous drive.
Intel is now using 16GB flash packages instead of 8GB packages from the original drive. Once 34nm production really ramps up, Intel could outfit the back of the PCB with 10 more chips and deliver a 320GB drive. I wouldn't expect that anytime soon though.
The old X25-M G1
The new X25-M G2
Low level performance of the new drive ranges from no improvement to significant depending on the test:
Note that these results are a bit different than my initial preview. I'm using the latest build of Iometer this time around, instead of the latest version from iometer.org. It does a better job filling the drives and produces more reliable test data in general.
The trend however is clear: the new G2 drive isn't that much faster. In fact, the G2 is slower than the G1 in my 4KB random write test when the drive is brand new. The benefit however is that the G2 doesn't drop in performance when used...at all. Yep, you read that right. In the most strenuous case for any SSD, the new G2 doesn't even break a sweat. That's...just...awesome.
The rest of the numbers are pretty much even, with the exception of 4KB random reads where the G2 is roughly 11% faster.
I continue to turn to PCMark Vantage as the closest indication to real world performance I can get for these SSDs, and it echoes my earlier sentiments:
When brand new, the G1 and the G2 are very close in performance. There are some tests where the G2 is faster, others where the G1 is faster. The HDD suite shows the true potential of the G2 and even there we're only looking at a 5.6% performance gain.
It's in the used state that we see the G2 pull ahead a bit more, but still not drastic. The advantage in the HDD suite is around 7.5%, but the rest of the tests are very close. Obviously the major draw to the 34nm drives is their price, but that can't be all there is to it...can it?
The new drives come with TRIM support, albeit not out of the box. Sometime in Q4 of this year, Intel will offer a downloadable firmware that enables TRIM on only the 34nm drives. TRIM on these drives will perform much like TRIM does on the OCZ drives using Indilinx' manual TRIM tool - in other words, restoring performance to almost new.
Because it can more or less rely on being able to TRIM invalid data, the G2 firmware is noticeably different from what's used in the G1. In fact, if we slightly modify the way I tested in the Anthology I can actually get the G1 to outperform the G2 even in PCMark Vantage. In the Anthology, to test the used state of a drive I would first fill the drive then restore my test image onto it. The restore process helped to fragment the drive and make sure the spare-area got some use as well. If we take the same approach but instead of imaging the drive we perform a clean Windows install on it, we end up with a much more fragmented state; it's not a situation you should ever encounter since a fresh install of Windows should be performed on a clean, secure erased drive, but it does give me an excellent way to show exactly what I'm talking about with the G2:
| PCMark Vantage (New) | PCMark Vantage HDD (New) | PCMark Vantage (Fragmented + Used) | PCMark Vantage HDD (Fragmented + Used) | |
| Intel X25-M G1 | 15496 | 32365 | 14921 | 26271 |
| Intel X25-M G2 | 15925 | 33166 | 14622 | 24567 |
| G2 Advantage | 2.8% | 2.5% | -2.0% | -6.5% |
Something definitely changed with the way the G2 handles fragmentation, it doesn't deal with it as elegantly as the G1 did. I don't believe this is a step backwards though, Intel is clearly counting on TRIM to keep the drive from ever getting to the point that the G1 could get to. The tradeoff is most definitely performance and probably responsible for the G2's ability to maintain very high random write speeds even while used. I should mention that even without TRIM it's unlikely that the G2 will get to this performance state where it's actually slower than the G1; the test just helps to highlight that there are significant differences between the drives.
Overall the G2 is the better drive but it's support for TRIM that will ultimately ensure that. The G1 will degrade in performance over time, the G2 will only lose performance as you fill it with real data. I wonder what else Intel has decided to add to the new firmware...
I hate to say it but this is another example of Intel only delivering what it needs to in order to succeed. There's nothing that keeps the G1 from also having TRIM other than Intel being unwilling to invest the development time to make it happen. I'd be willing to assume that Intel already has TRIM working on the G1 internally and it simply chose not to validate the firmware for public release (an admittedly long process). But from Intel's perspective, why bother?
Even the G1, in its used state, is faster than the fastest Indilinx drive. In 4KB random writes the G1 is even faster than an SLC Indilinx drive. Intel doesn't need to touch the G1, the only thing faster than it is the G2. Still, I do wish that Intel would be generous to its loyal customers that shelled out $600 for the first X25-M. It just seems like the right thing to do. Sigh.
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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.