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.