The SSD Relapse: Understanding and Choosing the Best SSD
by Anand Lal Shimpi on August 30, 2009 12:00 AM EST- Posted in
- Storage
Power Consumption
SSDs are at their highest power consumption when performing large file sequential writes. The majority of the power consumption comes from writing to the NAND flash and when you’re doing sequential writes you have more flash devices engaged at a time. Thus my peak power consumption test involves measuring power used over the 5V rail while the drives perform my 2MB sequential write benchmark in Iometer and at idle of course.
First, the idle numbers:
The Samsung and Indilinx drives use the least power, while the Intel drives use the most out of the SSDs. Intel honestly just needs to stick some power gate transistors in front of the controller and flash to curb power consumption at idle. They are all still lower than a mechanical drive, and much lower than a 3.5" HDD.
It's also worth noting that given the order of magnitude performance advantage these drives hold over traditional hard drives, they spend far more time at idle than their mechanical counterparts.
Under load the SSDs use anywhere from 2.5 - 3.5W, the exception being the Indilinx SLC drive which comes in at under 2W. Power consumption is roughly half if you switch to a random write workload, and the standings also switch places. While Intel's X25-M G2 draws less power than the OCZ Vertex Turbo in the sequential write test, it draws more power in a random write workload:
| Random Write Power Consumption | Min | Average | Max |
| Intel X25-M G2 160GB (MLC) | 1.55 W | 1.60 W | 1.7 W |
| OCZ Vertex Turbo 128GB (Indilinx MLC) | 1.13 W | 1.17 W | 1.21 W |
As I alluded to before, the much higher performance of these drives than a traditional hard drive means that they spend much more time at an idle power state. The Seagate Momentus 5400.6 has roughly the same power characteristics of these two drives, but they outperform the Seagate by a factor of at least 16x. In other words, a good SSD delivers an order of magnitude better performance per watt than even a very efficient hard drive.
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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.