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Thread: Hard Drive Issues in a Vehicle Computer

  1. #1
    Neither darque nor pervert DarquePervert's Avatar
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    Hard Drive Issues in a Vehicle Computer

    • Should I mount my hard drive vertically or horizontally?
      There's been a lot of discussion in the 19 months I've perused these forums about how to mount a hard drive for a vehicle PC environment. There have been a lot of very good points raised by people with knowledge in this area.

      The basic question is whether mounting the hard drive vertically or horizontally would increase the longevity and stability of the hard drive. The answer is inconclusive. Users have had drives mounted vertically with no problems and horizontally with no problems, both over the long-term.

      The question stems from the possibility of the drive heads breaking the cushion of air they ride on and coming in contact with the surface of the platter, which would damage the platter, causing data loss (at best) and hard drive failure (at worst). That seems to be a logical concern, especially when driving over poor-quality roads or even off-road for those that are so inclined, however there is no evidence that horizonatllay-mounted hard drives are more susceptible to shock-related damage than vertically-mounted ones.
      Now, it's also logical that the flud in the bearings for the platters would pool at the bottom of the bearing compartment in a vertically-mounted drive, causing extra friction, heat buildup and premature failuyre of the drive. Again, while it sounds logical, there is no evidence to support this.

      So how should you mount your hard drive? In whatever orientation fits the space available for your project.

    • How can I protect my hard drive against excessive shock and/or vibration?
      The common idea is to use rubber or silicone grommets between the hard drive and the mounting points. I used the silicone feet from my Shuttle case as the washers for my project. They are about 3/8" tall (I haven't measured, so I don't know exactly). Additional rummber grommets/washers could be used when mounting the PC case (if you use one) as well.

      Others have used elastic bands (a.k.a. bungee cords) to suspend a hard drive inside an enclosure. This may seem like a good idea until one of the elastic bands breaks or comes loose from its mounting point and treats your drive like slingshot ammunition. There is also the possibility of the elastic bands developing a harmionic vibration that could also decrease the life of the drive if it persists for a long period of time. I wouldn't recommend this as a mounting solution for those reasons.

      Still others have used anti-static closed-cell foam as a cushioning material between the hard drive and the mounting location. This doesn't provide as much shock amsorption as rubber/silicone grommets, but provides some. It isn't recommended to cop up your sleeping pad for camping. Make it anti-static foam to prevent static from destroying your shock-protected drive.

    • Will extremely cold or hot temperatures cause problems with my hard drive?
      You bet. Every electronic component has an optimum temperature range for operation. If the temperature is far enough outside that range, the component won't work.

      Hard drives have fluid bearings. Any fluid can freeze if it gets cold enough, including the lubricant inside the hard drive. If the hard drive starts to spin up (which happens as you boot your PC), the platters will not turn because the fluid isn't viscous enough to allow the platters to spin at the proper speed. As a ruslt, your computer will either not boot at all with an error at POST or it will boot up and give data access errors once booted.
      The heat will have the opposite effect on the bearing lubricant, making it too liquid, and not providing adequate lubrication. This is less common than a hard drive in the extreme cold, but I have seen it happen. The poor lubrication will cause excess friction and heat and possibly drive failure.

      The simple solution is to not boot the vehicle PC up until the ambient temperature of the vehicle is inside the operational range for the hard drive. If your hard drive is in your trunk (or boot if your British), you may not be able to do anything about the ambient temperature. If you live in an area that gets extremely cold, I'd advise against mounting your hard drive in the trunk for this reason.

      Some have taken the steps to get their OS installed on a Compact Flash card and booting from that. It isn't going to speed up your PC much, if at all, but since the compact flash has no moving parts, it will boot in the cold temeratures that would render a hard drive useless. This isn't an easy process, however. YMMV.

      There are other solid-state drives on the market (or coming to market) that would serve the same purpose as the CF setup, however these tend to be very pricey, out of reach of most hobbyists. If you can lay hands on one of these, it would certainly be a good solution for HDD replacement.

  2. #2
    FLAC
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    Nice write-up, DP.

    For what it's worth, I've had two hard drives mounted in my computer in my trunk for over five years and they're still working fine. The drives are mounted horizontally just as they came in the computer. I've made no effort to protect them from shock or extreme temperatures. I'm not saying those efforts aren't advisable, only that I haven't done anything and the drives have survived.

  3. #3
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    Bugbyte's Avatar
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    The mounting direction has been the topic of continuous and sometimes furious debate on this forum. To date, people have presented a number of arguments about why a certain direction or method of mounting will or won't work but never proof one way or the other.

    If you want to read some of these debates, try these links. Make sure you check the date of the original post for fun. Some of them go back a ways.

    1. Here's a spirited one that starts in 2003 and has an example of a shock protection system. The thread originator concludes that horizontal gave no problems while vertical did.
    2. Here is one where the argument has a "does so!", "does not!" flavor to it.
    3. Here is one that shows how a member has built a shock mount for his drive. Post 57 & 58 show another way to do it. Read post #14 where MatrixPC notes that he used to use a rubberized shock mount but it caused his drives to skip.
    4. From the same thread above, DeadWeasel explains in detail why you shouldn't worry about shock.
    5. Yet another one.
    Quote Originally Posted by ghettocruzer View Post
    I was gung ho on building a PC [until] just recently. However, between my new phone having internet and GPS and all...and this kit...Im starting to have trouble justfiying it haha.
    Want to:
    -Find out about the new iBug iPad install?
    -Find out about carPC's in just 5 minutes? View the Car PC 101 video

  4. #4
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    Here's some links to threads that I posted in another thread that asked these same questions:

    Harddrive - Vertical or Horizontal

    "Soft" hard drive mounting....

    Too much bass for my pc case?

    Off-roading with a CarPC

    Newb with a few questions.

    hard drive mounting questions

    Frequently Asked Questions

    Protecting HDD from powerful subwoofer vibrations?

    Mounting hard drive flat rather than upright

    All within the first page of the search feature when using 'hard drive vibrations' as the search key.

    'Hard drive vibration' revealed even more:

    SERIOUS Vibration Insulation

    Hard Drives?

    Carputer next to the subs?

    HDD vibration solution

    subs and Computers? do they mix?

    That's what I found, there's more but I have to go to lunch.
    Jan Bennett
    FS: VW MKIV Bezel for 8" Lilliput - 95% Finished

    Please post on the forums! Chances are, someone else has or will have the same questions as you!

  5. #5
    Newbie
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    I am a new member, just signed up. Thinking of a carPC for my Z06 Corvette. Reading through the FAQs.

    I make hard drives for a living. Have been in this business for 20 years. Here is some info you can take as fact...

    HDD operation is heavily influenced by temperature. Bearings, both in the spindle motor (either BB or FDB) and in the rotary actuator (BB) rely on lubricants. The lubricant's viscosity, like any lubricant, changes with temperature. Thicker when cold, thinner when hot. Colder temperatures are more problematic, since the increased viscosity significantly "stiffens" the bearing, resultant drag is high and motors may not be able to achieve their minimum operating speeds. But high temperatures can cause the lubricants to fail, with obvious consequences.

    In addition, mechanical dimensions of the entire HDD assembly will change as a function of temperature (the HDD components are primarily comprised of Aluminum and Stainless, which have different coefficients of thermal expansion. This usually isn't so much of a problem, since the mechanical tolerances allow for this, but it can result in reduced performance. And significant temperature excursions can cause glue bonds (bearing cartriges are usually glued together) to fail and/or result in brunelled bearing races.

    The recording heads are also affected by temperature. The critical parameter is something called "Fly Height", the distance above the surface of the disk at which the "Slider" rides on it's "Air Bearing". Too high (usually colder) can cause write and read errors. Too low (usually, hotter) can result in contact between the Slider and platter, permanently damaging the HDD.

    The disk surface itself is coated in a fine layer of lubricant. It's designed to provide some protection if the recording head (Slider) contacts the disk surface. Temperature effects this lubricant like any other. In particular, at very high temperatures the lube can "spin off" the disk, reducing the effectiveness of the protecting layer.

    The magnetics and electronics all behave differently as a function of temperature. Usually, the HDD is designed to compensate for the effects. But operating the HDD outside it's temperature limits can exceed the range of compensation, typically leading to read and write errors.

    As a general rule, higher temperatures are worse in terms of HDD longevity but the HDD should generally work OK up until the point when something breaks. At cold temperatures the HDD may not work at all, but it is unlikely that attempting to get it going will do it any harm, it just won't work.

    Mechanical shock and vibration are the enemies of HDD reliability.

    The recording head consists of a "Slider", which flies over the surface of the spinning disk (think of an Air Hockey puck and you'll get the idea). The Slider contains the read and write elements that allow data recording (think of a Cassette Tape recorder and you'll get the idea). The Slider is attached through a "Suspension" to the rotary actuator. The HDD positions the Slider at different radii across the Disk by rotating (think of a Phonograph Tone Arm and you'll get the idea). The "Air Bearing" created by the flying Slider is fairly robust, but shocks in the Z direction can force the Slider to contact the disk surface, and that's bad.

    Desktop and Server drives use Contact Start Stop, the heads actually land on the disk surface when the disk is stopped. Mobile drives use something called "Ramp Load", the heads are lifted off the disk when the disk is stopped. For this reason, it is not a good idea to use a Desktop HDD in a mobile application. Desktop HDDs are prone to a kind of damage called "Head Slap" when stopped, and so are less robust when it comes to tolerating the types of mechanical shocks likely to be seen in a mobile application.

    Data is located on the disk surface in a series of concentric tracks. Each track is divided in to segments called "Sectors" (think of Pizza slices and you'll get the idea). To locate data on the disk, the HDD rotates the Actuator to the target track, and then it waits for the desired Sector to rotate under the Slider and past the read/write elements.

    The HDD has to control the Actuator very accurately, track widths are measured in microinches. Linear motion (in the X, Y, or Z direction) has very little effect on the HDD's ability to "Track Follow", the Actuator is balanced, but rotary motion (rotation around the Spindle Motor's Z axis) is very difficult for the HDD to handle. The HDD will monitor it's track position and abort read and write operations (and subsequently retry) if it's straying too far, so usually the worst effect of linear or rotary shock is reduced performance. However, very large shocks can result in mis-reads or mis-writes (the Slider strays on to an adjacent track while reading or writing).

    Vibration can excite resonances in the HDD's mechanical structure. Resonance has the effect of magnifying the vibration and it can result in the same kinds of errors and lost performance that large shocks will cause.

    An HDD is a fairly delicate, precision mechanical assembly. Banging it around does physical damage and will lead it to an early demise. Luckily, the suspension of your car does a good job at absorbing or attenuating the kinds of strong, high-frequency shocks that are likely to do the most damage to an HDD. Fancy isloation systems are not generally necessary. But for the best performance, it is important to mount the HDD in a location that is as vibration free as possible. Isolation mounts can be beneficial in achieving this aim.

    Also if possible, mounting the HDD vertically (on edge, not flat) will prove advantageous. Most of the strong shocks transmitted through the car's suspension are in the Z axis (up/down). The HDD is most sensitive to mechanical shock in the Z axis, least in the X and Y. If you mount the HDD vertically, you're aligning the most robust HDD axis with the strongest source of excitation and you are less likely to experience mechanically induced problems or outright failures.

  6. #6
    FLAC
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    Wow, thanks for that excellent explanation.

    I can only speak from personal experience. I've had a carputer for about 7 years now. I live in VA, USA, where temperatures reach 100 degrees in the summer and dip into the teens in the winter. I have my computer in the trunk with the drive mounted horizontally and have used no shock protection of any kind. I have experienced no hard drive failures during that time.

  7. #7
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    I didn't mean to imply that you would have problems, only that if you're looking maximize your HDD's reliability, vertical is better.

    That being said, if you've had a laptop 2.5" HDD in your car for the last 7 years, you're doing *really* well. That's far beyond the design-life of the HDD, especially given it's operating in a much harsher-than-normal environment!

  8. #8
    FLAC
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    They've actually been desktop drives (3-1/2"?). I guess my post was a little misleading because it hasn't been the same drive for seven years. I've had to upgrade my drive a couple of times due to insufficient storage capacity. But in the seven years that I've had drives in my car, I've never had a failure. I am lucky, though drives are so cheap nowadays that it's not the end of the world if one goes.

  9. #9
    FLAC W3bMa5t3r's Avatar
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    I knew there was a reason I had the gut feeling that the laptop drives would be better, the ramp load. Though I'll be keeping allll my music on the desktop drive since a laptop drive big enough for all that is too freak'n expensive, but the os is staying on a laptop drive. Great info. Thanks.

  10. #10
    Maximum Bitrate eugenen's Avatar
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    If anyone has ever taken HDD's apart you will understand why vertical or horizontal makes no difference. You will see that the arms that hold the heads are spring loaded and actually press the teflon "bearing" surrounding the head against the platter. When the platter spins up to speed the bearing floats on a microscopic thin layer of air but when the platter spins down the teflon bearing lands on the platter. The head is in side the teflon and never touches the platter.
    Also the fluid in the spindle and head bearings won't run down to the bottom of the bearing if vertical because the bearing is full of fluid. Take a half empty bottle of water and put the lid on and turn it upside down and the empty space moved to the top as the fluid goes to the bottom. Now fill the bottle completely to the top and put the lid on and turn it upside down and since there was no empty space before there is no empty space now.

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