Wednesday, July 2, 2008

Tom Gets it Wrong: SSDs vs HDs

I would dare saying it's almost horrifying to see how a faulty test can cause such mayhem.

The issue is that there was this "test" on Tom's Hardware comparing SSDs with traditional rotating media Hard Drives that showed that SSDs actually cause you laptop to have less battery life instead of more.

What they fail to say is that their "test" run continuously, and the results they get are similar to proving that you get faster to your destination driving at 100 Mph than 50Mph!

The SSD drive drains the battery faster, ok... but how many times did it run the test compared to the traditional HD?

That's a piece of the test they failed to include. If the the SSD run the same number of cycles as the HD did, there's no doubt it would have done so in a lot less time, and you'd still have a powered laptop long after the HD test case drained its battery.

From their own power consumption charts, you can easily see that even if SSD power use in active mode is similar to a HD, you have to keep in mind that the active duty cycle is much lower in a SSD. (Accessing data, reading/writing, which would take 0.5 seconds in a traditional HD could probably be done in 1/5th the time on a SSD.)

So, lets hope Tom's Hardware can run those tests again, but in a way that gives accurate results - or show the missing parts of the test results, to see how more efficient the SSDs were.
Unless they're trying to tell me that, during the time the HD is spinning for the extra 1:30 minutes, the SSD is consuming more power?

via [Engadget

Tom's Hardware acknowledges the SSD test was flawed.


  1. Toms is actually comparing cycles: In one graph they multiply drive performance with battery life. Here the high performance SSD's are almost competitive with the hard drive.

    I don't know the tests, but I don't think the assumption of continous performance is correct: When surfing or typing text on laptops with enough RAM, you are not much accessing the drive at all. Thus, the idle time of hard drive vs. SSD becomes significant.

    Also the speed with which idle to performance can happen is significant for performance. I don't think Toms take this into account.

    If you are watching locally stored movies in mp4 format at 2MB/s you would not really stress a harddisk if you have enough RAM, again, idle time is important.

    When starting applications, you really want high performance and here SSD's may make a difference.

    BTW: I'm typing this on a macbook air with harddisk and I don't think the SSD trade-off is worthwhile yet.

  2. First of all, thanks for your input Icebird.

    However, I have been using laptops for several years, and have yet to have used one that kept in "idle" mode while working (even under "light" operation circumnstances.)

    Even in with 4GB Ram, simply typing a word document, the hard drive is frequently "acessing" the hard disk, preventing it from idling - (and I'm the kind of person that doesn't keep uneeded services running in the background.)

    If it is really worth the premium price - that is another matter.
    But thankfully SSDs are dropping fast - 32GB SSDs are now reaching the $150 point; and in some cases, SSDs *do* make a difference.

  3. I guess it depends on OS and software. MS Word on Windows could well stress a system.

    Programming in a light text editor with intensive compile runs every 5 minutes would have a different profile.

    I watched Activity Monitor while browsing a few pages. Spikes of write activity followed by absolute silence for several seconds.

    If a drive can enter idle mode in less than second after activity this can be significant, but if idle is not allowed if activity happens, say, every 5 seconds, then idle won't matter much. I don't know how SSD's or hard drives behave in this respect, but as Tom points out, hard drives need not use much power just because they are active (no seek).

  4. Well, I don't even understand why Flash SSDs can use more power in idle mode than regular HDs - if they can hold their data without any power, there's no reason to behave like that.

    (In a worst case scenario, an SSD should require the power needed for the drive electronics - as much as a regular HD - minus the spinning hard drive.)

    No matter what, HD have been improved for decades, while SSDs are a lot less mature.

    I'm sure in the coming months, lots of improvements will show up on SSDs, including much more efficient power management.


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