www.tomshardware.com/reviews/ssd-hdd-battery,1955.html
Intel's new mobile platform Centrino Duo brings dual core processors to notebooks. This new architecture is supposed to be noticeably faster, while not reducing battery life. We find that while the first part of this proposition appears to be true, we can't endorse the second part without some reservations.
There has been a drought in the supply of lithium ion batteries required to power notebooks that has been squeezing supply of notebooks to the growing market. It should now be over in time for Christmas, according to one executive in the industry.
We predicted performance gains for Flash solid state drives. Mtron's 32 GB SSD proves that Flash drives can now beat the pants off mechanical hard drives, even though some rough edges still require smoothing.
Memoright has achieved an important milestone with its flash SSD: the devices performance is truly better than that of any competing hard drive we have seen to date. Any skepticism one might have had about SSDs future should now be put to rest.
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.
SSDs easily outperform conventional hard drives today (SLC = single level cell). However, we have discovered that the power savings arent there: in fact, battery runtimes actually decrease if you use a flash SSD. Weve looked at almost a dozen different flash SSDs from seven vendors over the last few months, and measured acceptable or sometimes even disappointing power requirements with most flash SSDs. In an effort to determine the actual impact on notebook systems, we took four SSDs that we had available in our test lab, and ran a series of Mobilemark benchmark runs on a Dell Latitude D630 notebook. We found runtime differences of up to one hour when using a flash SSD compared to a high-performance 7,200 RPM 25 notebook hard drive. Flash is cool, because its expensive, and because it does provide significant performance advantages (when SLC flash is used). But while our results are interesting for most users, they will be shocking to road warriors. You will see very clearly in the benchmark section that theory and real life are sometimes entirely different. We still believe that flash-based drives will be the future for the performance segment, but they must not become a key component for energy-efficient notebooks and ultra-portables where performance is secondary as long as their average power consumption is higher than that of conventional 25 notebook hard drives. In fact, even a high-performance 7,200 RPM 25 drive provided better overall battery runtime than most of the flash SSDs we put through the Mobilemark test.
So many power saving features have been implemented into HHDs, but SSDs are very young. I'm sure that at least some companies understand and recognize this, and are developing new features to help with this. Technically, it may not be that the claim on "energy efficiency" is indeed true. the efficiency could be measured in mW spent per Kb of information retrieved. For example, a HHD in sequential reading uses up very little power, but also retrieves only the information needed. It could be that the SSD's have to check many more bits of data in order to find the information requested. I believe the salespeople took a logical step in claiming energy improvements, due to the fact that it uses no visible motors. However, this testing (at least in my eyes) shows that they have simply "forgot" to check up on the actual statistics. It could also be that as cell density increases, read and write speed will increase as the power consumption stays almost static. Since the 18' SSD eat up almost the same number of watts for the larger SSDs, it could be said that the power itself is not being consumed in the actually memory itself, but in reality the controller that access the information. IT is very very interesting to see the small difference between the different sizes of SSDs, and might be a window into seeing the full potential of these devices.
The overview seems to be reasonable but comparing to the benchmark results it looks quite different. Just look at the Battery Runtime and Energy Consumption charts!. The SanDisk SDD drive at LOAD requires 10 mW while Hitachi HDD requires 11 mW at IDLE (for me it means in POWER SAVING MODE). So if laptop work time with Hitachi HDD is longer than with SanDisk SSD the benchmarks seems to be VERY unreliable.
For example, better working read and write caching would be a boon: since SSDs have pretty much no access time penalty, a large write cache becomes much less interesting - grouped writes, optimized for the SSD's internal cache, may reduce the time the system stays on. Deactivating the swap file (or not making use of it as often as Windows does) would also probably reduce 'active' time quite a lot. It would be interesting to see the difference when using a more disk efficient OS: I dunno, any Linux-based distribution? After all, Dell provides Ubuntu on some laptops and UMPCs are currently often provided with SSDs - so it would actually be quite relevant. Typically on these systems, the swap gets written to only when the RAM reaches around 60% (or more) use, while Windows preemptively copies 'dirty' RAM pages to swap and frees RAM only when actually needed (leading to faster RAM pages freeing, but also frequently unnecessary disk access). Running these tests again (with all disks and some extra RAM) with: - Windows using no page file - Linux with a swap partition - Linux with deactivated swap may give us a better idea of SSD advantages. About those who would complain that relying on RAM instead of swap is not possible: - current systems (except lower Windows editions) can handle more than 4 Gb of RAM; Windows 2003 for example, does support PAE and extended memory sizes (64 Gb) - if you have cash to pay for an SSD, you have cash to pay for 4 or 8 Gb of RAM Of course, that doesn't prevent SSD makers from looking for extended power schemes (reads should require less power than writes, and idle should require no power) and a low power SATA mode (allowed by shorter cabling) could be designed.
skittle This SHOULD have been included in the article... Each module includes a robust and refreshed set of applications and can be run individually to show battery life in a greater variety of specific scenarios.
JonathanDeane I am thinking the idle power of an SSD could in theory be zero since it is a flash drive and there is no "spin up" this is interesting... seems the drive electronics (not the actual flash chips) are eating allot of juice. An OS patch with an option to put the drive to sleep when inactive for something like 1 second seems like it would save power and since the power on should be instant have almost no negative impact.
mastrom I agree with Fritz, I think it's very important to make sure the work the laptop does with SSD and HDD is the same. And I'm not sure having a laptop run a benchmark until it runs out of battery comes close to real world usage. Playing a movie again and again would probably be a simple and clean test that is not questionable. At the moment I'm not convinced that your conclusions are correct.
pschmid As I pointed out in the conclusion, an application scenario that does not tax the drive very much can very well lead to increased battery runtime. Think this way: You hibernate the system, because you have to move location.
Mtron Flash SSD drive half a year ago - and I saw a decrease in battery runtime of my Lenovo T60 that could not be attributed to wear of the battery. If you want to send me more specific suggestions on additional tests, such as specific applications, I'll be happy to run them when we compare the next Flash SSDs.
If you plainly compare IDLE and LOAD wattage, yes, SSDs SHOULD be using less energy than conventional platter drives. But what you have forgotten is the read/write performance. You have to count that in when measuring power consumption. For example, if the SANDISK SSD takes 2 seconds instead of 1 second for TravelStar to read or write the same data...
|
http://csua.com/feed/