Are SSDs Really More Power Efficient?

Bakasama writes "Tom's Hardware compared the power performance of several available SSD cards with a Rotating HDD that was chosen specifically for its poor power efficiency. The results seem to fly in the face of current wisdom. 'Flash-based solid state drives (SSDs) are considered to be the future of performance hard drives, and everyone seems to be jumping on the bandwagon. We are no exception, as we have been publishing many articles on flash-based SSDs during the last few months, emphasizing the performance gains and the potential power savings brought by flash memory. And there is nothing wrong with this, since SLC flash SSDs easily outperform conventional hard drives today (SLC = single level cell). However, we have discovered that the power savings aren't there: in fact, battery runtimes actually decrease if you use a flash SSD.'"

Comments

More power but only while being hammered?

[gmack]

So if your not a laptop user and aren't currently benchmarking your drive how long will it last?

What is the power usage for real world office/ web browsing type use?

Obviously that cannot be!

[Anonymous Coward]

Impossible! Those results are obviously wrong!! Now go back and do the experiment. Keep doing different experiments until we get the desired results!

How dear you try and endanger my stock portfolio?!

Re:Obviously that cannot be!

[hclewk]

Unfortunately, the article comes to miserably faulty conclusions, and nobody seems to have noticed it. One thing everybody needs to note is this: the test that Tom's ran was designed to run a program to completion over and over again. All that Tom's came up with, thanks to that test, is that the computer with the SSD ran out of power faster. What they SHOULD have noticed, and what any sane and logical tester would have done, is counted the number of times the program RAN. A system with an SSD will run the program a significantly higher number of times because of its increased speed and lack of moving parts. With the higher number of runs, the CPU STAYS MORE ACTIVE, sucking more power out of the system and thus causing it to power down earlier. The only reason the HDD system died later is because the CPU idles waiting for it to retrieve data. The SSD may have chewed up your battery faster, but it did, comparatively, run through that program a BUNCH more times. I am willing to bet the work per watt was much better out of the SSD system than the HDD - and once again, Tom's Hardware's scientific testing system proves itself anything but.

Still too new

[ArcherB]

I believe that much of the problem is that SSD's are still a new technology compared to rotating disks. Right now, engineers are more concerned with increasing capacity and just making the damn things work. These are much more important than efficiency. As time goes on and the technology gets more mature, efficiency will get more attention from engineers.

running a synthetic benchmark 100% of the time...

[Anonymous Coward]

I wish they would measure power usage under conditions that many notebook computer users actually use them in, which does not include running synthetic benchmarks on their computer 100% of the time it's running. Of course, if you keep the machine writing to the ssd constantly then it's not going to show power savings. But how many mobile users' usage patterns include constant reading from and writing to disk?

Sweet

[Anonymous Coward]

Now I'm even happier that I paid the extra $1300 for the SSD option in my MacBook Air.

That way it will run out of battery sooner, leaving me free to use a real computer.

Not so good benchmark

[marc.andrysco]

I believe this comment from the article could explain some of this away.

'There could be a systematic error in the benchmarks shown: if the flash based "disks" are faster then the whole system CPU/MEM/Chipset would draw much more power with flash "disks" compared with conventional disks - just because the benchmarks could run more often in the same time.

Maybe one should compare something like playing video from disk where it is assured that the systems do precisely the same work?'

Re:Not so good benchmark

[marc.andrysco]

Yeah, another post mentioned that a SSD's power consumption during load is higher than another magnetic disk on idle... here it is:

"The SanDisk SDD drive at LOAD requires 1.0 mW while Hitachi HDD requires 1.1 mW at IDLE"

Of course, benchmarks are always a better indicator. Also, to be clear, as mentioned in the article (which I'm sure nobody else read), the test was performed by repeatedly running a benchmark on the system until it ran out of battery, so the test with the SSD is likely to have run the test more often.

Re:Not so good benchmark

[afidel]

Actually two out of four SSD's reviewed used MORE power when idle than the 7200rpm drive, that's just stupid. The Sandisk used about 60% less, so there's a reason to go with the name brand in this case, they do a heck of a lot more R&D than simply throwing some components together off the shelf.

Re:running a synthetic benchmark 100% of the time.

[Rakshasa Taisab]

Exactly... The thing about spinning platters is that it takes energy to start up _and_ keep it spinning. So obviously doing read/write 100% of the time would bias towards the conventional hard drives.

Hell, even read/write 10% of the time is too much for normal usage.

Author = Clueless and Stupid

[slaker]

I have a 32GB SSD in my T61. My real life usage shows that I get between 30 and 45 more minutes of battery life out of my SSD-equipped notebook than on my other T61, which has a 160GB 7200rpm drive in it, when both of them are on the "medium" power saving setting in Windows.

Power Efficient? They can barely aim!

[SDF-7]

Seems unlikely to be all that power efficient to me... hauling around that huge bulk, and it sure didn't seem like Executor really made all that difference at the Battle of Endor from a capital ship perspective. (Probably because most turbolaser batteries seem to have really lousy guidance,
after all).

Oh... you meant those SSDs.... my bad.

Old and inaccurate

[jlp2097]

The article states nothing new - there are two very interesting blogs from Lenovo which already stated the same in August 07 (!). To quote:

Solid state HDDs promise to save power compared to traditional hard disk technology. And they will. However today's generation of SSDs have no power savings benefit compared to traditional HDDs. The big reason is that current SSDs with a Serial ATA interface are actually Parallel ATA hard disk drives with a serial bridge chip. They don't offer support for low power interface states and the architecture has a potential for data-losing error conditions when recovering from a low power state like suspend or hibernate. In the future, there will be native SATA solutions which will solve many of these problems and will at the same time offer a real power savings benefit which should increase battery life.[1]

An updated quote from a newer blog:

Power Consumption - All SSDs are going to save you battery life on your notebook, but some will save you more than others. Again, the native SATA drives will give you better battery life.[2]

To summarise: old news and mostly outdated with very recent SSD drives.

[1]: SSD part 1 (Aug 07)

[2]: SSD part 2 (March 08)

Check Page 14

[pjrc]

In TFA, there is a graph on page 14 with power consumption measurements for the 5 drives tested.

The SanDisk SSD shows 1.0 watt active, 0.5 watt idle.

The Hitachi drive (magnetic) shows 3.2 watts active, 1.1 watts idle.

So even if the SanDisk drive spent 100% of its time in active mode and the Hitachi drive was always idle, the SanDisk drive should still provide longer runtime.

However, their runtime test (page 12) shows 7:03 runtime with Hitachi, 7:02 with the SanDisk.

All they have to say about this is:

Most of the power consumption measurements are in line with our results in Mobilemark 07. However, it has become clear that idle and maximum power do not provide the full picture when we talk about flash SSDs.

Well, something clearly is wrong here.