Are there any studies or evidence which show that mounting a hard drive horizontally is better than vertically for the lifespan of the device? Or upside down, or any direction for that matter.
The quotes in this thread from WD and Seagate suggest not.
To precis the link: Seagate, Maxtor and WD drives can be used in any orientation including upside down.
Orientation does not affect a drive. Think about iPods with hard drives. They are changing orientation all the time. The most important thing in a drives life is writing to the sectors. Current versions of NTFS do a write leveling (Novell was doing it in the 80's) that will use all the disk surface. Older OS's and file systems under Windows reused portions of the disk when files were erased.
With write leveling the center of the disk gets used as well as the outsides. This will increase the disk life for multiple reasons that are off this topic.
I've never heard of that being a problem.
With older drives however, I do remember the life of a drive coming to an end if it had been running in one orientation for a prolonged period of time, and then turned. For example a server that had been running for several years, when relocated and rotated into a new position, soon after disks would begin to fail.
But I haven't seen that with newer drives.
Early PC hard drives such as the ST506 were based on stepper motors. These did not have any feedback mechanism for head vs track position and thus had to be used in the same orientation that they were formatted in. Voice coil harddrives have a feedback loop that allow them to correct for errors such as changes in orientation.
I would expect that a vertically aligned drive will have to expend a small amount of power to correct for the effect of gravity in a manner that a horizontally aligned drive would not. However since as at least as many disk arrays seems to be vertically oriented as horizontal, I would expect such an effect to be minor.
Vertical is fine for the life of the drive if you need it. Enterprise class storage arrays often have the drives mounted vertically.
From a purely mechanical engineer's point of view, drives do have their head positioned in a certain position to the cylinders. If their heads were heavy, and sagging was a problem I'd say that horizontal position would be better. But those masses are neglieable, so it probably doesn't matter even in most idealistic test cases.
Conclusion: don't worry about it.
I have found that, when recovering a failing drive (one that sometimes spins down after power-up, or is excessively noisy, or that recalibrates with a click every second), they can be encouraged to spin up & stay up and running if you do re-orient them.
Another weird but wonderful trick is to put them in a freezer for a while. When the drive is powered back on it can generally be read for a while until it heats up again. You can extend their "cool" operation by putting one of those "freezer bricks" on top of the drive. Of course you have to watch out for condensation so plastic bags & tea towels are useful too.
I have fibre channel storage arrays here that mount both vertically (FC) and horizontally (FATA). If the big-boys don't care, then there isn't a fundamental difference.
The one area where it might come into play is changing the orientation halfway through the drive's life. That might cause a slight misalignment. However, with drive densities where they are these days read heads are doing statistical analysis anyway to figure out which block it is reading, and a slight misalignment is probably 'noise' in that analysis. It may have mattered more back when densities were in the 2GB range, but not when we're throwing around 1TB SATA drives.
My company makes systems where a PC is mounted in an industrial control cabinet. In most cases the HD in the PC is in a vertical orientation.
Since we had some drive failure issues we tried to see if there is a correlation between the orientation and failures. The conclusion, though based on very limited number of cases, was that the orientation had no influence on failures.
Heat and vibrations are the main causes of the failures probably.
From my own personal experience I would say that horizontally is better.
I had my drive for over 2 years now. It was only a few weeks ago that it started to get stuck (while playing a video file it would get stuck after a minute ) . It started making loud noises (louder than usual) as well. Then a few days ago it stopped showing the files in the drive. After restarting the files would show up again but when I open a file it gets stuck again. This kept happening many times.
I thought it was just Windows 7 screwing up but I tried accessing on Ubuntu, the same problem happens. Then I placed it horizontally and it honestly started working properly again. It doesn't get stuck and doesn't make those loud noises. The same video file also played without getting stuck.
I've been using my drive in a vertical position since I bought it. But the problems only started a few weeks ago. It would seem that the drive just got too old. But it started working normally after placing it in a horizontal position.
So I would say the orientation does matter.
That is just from my personal experience. My drive is a Seagate 1TB external drive which I bought in 2009. It came with a plastic stand which you use to place the drive vertically.
 The video file wasn't corrupted and i tried accessing other files in different locations too.
Just a comment on my experience. 5 years ago I had a Toshiba laptop. Some problem on the hard drive prevented it from booting. The temporary solution ended up being to turn it on its side. This was very temporary, since if I placed it level, it would slow down to less than a tenth of normal speed. Currently, I have a Gateway that has a similar problem - sometimes failing to recover from hibernate or sleep, and almost always (recently) failing to complete a reboot. 2 weeks ago, after multiple attempts to get it to boot, I turned it on its side. It booted immediately - at which point I made all the backups I needed. Yesterday, I had the same problem, and spent 24 hours trying to get it to reboot. Only after repeated failure did I remember to turn the laptop on its side. It booted immediately! It runs fine on a level surface, it's only the bootup that is a problem.
I've not yet replaced the hard drive, but will check it for integrity - probably using Spinrite - before discarding it.
From what I remember back in the day the orientation of a drive when it was formatted was the orientation the drive was suppose to run with. Of course this was well over a decade ago (over 2?). I have not seen any actual test of this, but it's fair to say it doesn't matter anymore.
I think we can believe the manufacturers with this one.
Actually I have found that if you have a hard drive that is starting to make a lot of noise, that if you just tip it to some angle other than 0° or 90° that it will run much quieter.
So in other words, if you're paranoid, you could tilt every thing by 15° to 75°.
I personally wouldn't worry about it unless you need to work with older drives.
I do a lot of computer service for peoples. About 18 years ago when I start in IT someone told me about position of hard drives and their lifespan. Since then I've been monitoring this and I almost certain that some hard drive positions are not good.
99% Faulty Laptop hard drives I do replace are from laptops where hard drive is mounted up side down. There is no way to change this as laptops have been designed this way.
Offender number one are TOSHIBA laptops. All laptops from this company which I cam across have hard drives mounted up side down.
You can use a drive horizontally or vertically, it is made to be used that way.
However, we* found that using a drive at a non-90°C degree (like with an angle of 30°), it wears faster, probably because it puts a bit more strain on the head when moving around.
*at the data recovery company I was working at
That really depends on the drive design so general rules are difficult. As many people said drives are generally expected to work flat or vertically either way.
However I seem to remember that some manufacturers advise against running drives upside down. and thinking of how drives are built I can see there might be issues.