HD vs SSD Power Consumption

Discussion in 'MacBook Pro' started by zachsternelson, Nov 15, 2010.

  1. zachsternelson macrumors newbie

    Nov 13, 2010
    Is it normal for SSDs to use the same or more power as a HD?

    An OWC Mercury Exreme Pro 40GB SSD uses 2.2W-2.5W when active.
    A WD SiliconEdge Blue 64GB SSD uses 2W when reading and 3.5W when writing.
    An OCZ VERTEX 2 40GB SSD uses 2W when in operation.

    A WD Scorpio Blue (5400rpm, 2.5") 250GB HD uses 2.5W when writing/reading.
    A WD Scorpio Black (7200rpm, 2.5") 250GB HD uses 2.5W when writing/reading.
    A Hitachi Travelstar 5K750 (5400rpm, 2.5") 500GB HD uses 1.4W when writing/reading.
  2. seydurin macrumors member

    Aug 3, 2010
    I read an article on Tom's Hardware where they bust the "SSD's use less power" myth. Supposedly they are only capable of consuming less power "in theory", when in reality they currently often use more power. Sorry if this bursts someone's bubble.
  3. alust2013 macrumors 601


    Feb 6, 2010
    On the fence
    It is normal actually. In the cases where it uses less power itself, it actually uses more CPU than a standard HDD would, thus drawing an equal amount of power to an HDD, if not more.
  4. deeddawg macrumors 604

    Jun 14, 2010
    I haven't read the Toms Hardware article, but the thing I'd like to see is how SSD's and HDDs are different in terms of how long they use the higher power.

    Since SSDs generally read and write faster than HDDs, in normal operation one would think they'd use less overall power.

    I did now look up the Toms Hardware article; it's about two and a half years old now. It would be interesting to see if the results remain the same in the face of the progress made in the SSD world.

    Still, it is a good point to remember; HDD's are very mature and the manufacturers have had time to really work out how to minimize power usage. I have no idea if the same is true for SSDs. I wouldn't look to SSD as way to extend battery life; get it for the speed of operation and the increased system usability.
  5. HotPopsicle macrumors newbie

    Oct 10, 2010
    Yeah, does that take into account the performance difference? In other words a SSD might use the same power as a HD, but if it performs at 2x-4x the speed you are getting a lot more for each watt. Also, the idle power draw on a SSD might be much less than the idle power draw of a HD which has to keep spinning that platter.
  6. dusk007 macrumors 68040


    Dec 5, 2009
    SSD are definitely better for the battery than HDDs. The first SSD Controllers had bad idle power consumption but newer ones are lower at idle than HDDs.
    They can enter different power modes faster than SSDs and usually stay Idle longer.
    An SSD wakes from Sleep almost instantly and after less than a second it is probably back to sleeping again or it reads a few hundred MB in a third of the time.
    HDDs do have more mature power consumption and in some situations like sequential read/write they actually use sometimes less power than SSDs, but once it gets a little random that almost always changes. In short HDDs have more different power modes but in they end they don't really help compared to SSDs.

    If you compare Server load where a SSD might run at high power draw most of the time you also need to compare it to equally fast HDDs which are at the very least Server HDDs that consume more than 10W and you probably need a few of them.

    Numbers for Notebook.
    A Kingston V+100 (same as MBA SSD)
    Idle 0.21W load 2-3W
    A good mobile HDD
    Idle 0,8W load 1,2-2W
    Sandforce SSD
    Idle 0,5W load 1,5W

    Idle power consumption is what really matters for maximum battery life. That is probably why Toshiba reduced Idle power as much as possible.
  7. mrsir2009 macrumors 604


    Sep 17, 2009
    Melbourne, Australia
    Being 2 and a half years down the track now, it is quite probable that SSD power consumption has improved. However the power saved would still not be so great that you'd buy a SSD just for that. Sure, it might save a few % when your using your computer all day, but the main reason SSDs are a good alternative to HDDs is the speed and durability factor (but mostly the speed factor) :)

    I'm getting a SSD before Christmas this year (for $300 or so) for the speed. Extra battery life would be very welcome, but if it consumed the same as a HDD I'd still buy it. I'm looking for quick bootups, snappy opening of applications, and no lag in firefox when opening tons of tabs (I have 11 tabs open at the moment) :p
  8. miata, Nov 15, 2010
    Last edited: Nov 15, 2010

    miata macrumors 6502

    Oct 22, 2010
    Silicon Valley, Earth
    What would be the affect of striping a pair of 120 GB SSDs (RAID 0) compared to a single 240 GB SSD?

    You are storing accessing the same amount of data either way. Right?
  9. Bill Gates macrumors 68020

    Bill Gates

    Jun 21, 2006
    Every write would be done twice. I'm not sure about reads using OS X's built-in software RAID since some controllers can read data from both drives at once; others from a single drive. RAID 1 is called "mirroring" by the way.

    Edit: If you meant RAID 0, power consumption will still go up since each drive consumes a small amount of power in an idle state.
  10. miata macrumors 6502

    Oct 22, 2010
    Silicon Valley, Earth
    Sorry meant RAID 0 -- not RAID 1. I'm pretty sure RAID 1 will use more power since data is written twice.
  11. dusk007, Nov 16, 2010
    Last edited: Nov 16, 2010

    dusk007 macrumors 68040


    Dec 5, 2009
    I wouldn't underestimate the power savings of an SSD.
    Take a 15" MBP that needs 9W when close to idle.
    8h 30m before 77Wh are dry. Take the difference between the Toshiba and a standard HDD.
    0,8W vs 0,21W ≈ 0,6W
    ≈> 9h 10m before 77Wh die.

    Almost no HDD unless you talk 4200rpm drives get below 0,8W some like the Momentus XT are at 1,3W idle.
    Now a little file is read from cache while browsing. CPU wakes up asks the HDD. Latency is worse when it was in idle and it is a laptop drive. 20ms until something comes back. An SSD has done the same thing in 1ms and it can return to 0,21W idle and the CPU can fall asleep sooner too. The HDD needs to park the head again and probably also waits a little before it enters idle sleep mode again. That probably makes for some difference if you have some disk access at all and considering how rare it is that an HDD ever shuts down after a long idle time those accesses happen quite often.

    I guess you can gain 30m to a full hour from an SSD with low workload.
    And one thing I would(still too expensive at the size I need 256GB at least) really appreciate about them is they are dead silent. If you live somewhere close to a forest and do some late night work you can hear the difference when the harddrive shuts down and while the display still shines everything is quite. That is really a nice feature. No one can say they cannot bare the noise of a 5400rpm drive but no noise at all is something completely different.
    Okay the fans in a MBP will still be running unlike some other notebooks where fans shut down completely but the harddrives usually are the loudest. I cannot make out the 2000rpm fans beside the noise of the harddrive. It never shuts down but i know from building desktop PCs that is fairly easy to cool everything dead silent (a 120mm fan at 600-700rpm is inaudible and often sufficient) but it is very difficult to silence HDD noise.
  12. miata macrumors 6502

    Oct 22, 2010
    Silicon Valley, Earth
    What about 2 120 GB SSDs in RAID 0 compared to a single 240 GB SSD or 7200 RPM 250 GB HDD?

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