Should I turn off my external hard drive when not in use?

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I've pondered this on end. Having worked for 25 years servicing disc drives (along with other equipment) I did observe that most failures in 'electronics' seem to occur on power down/up sequences. However 'mechanical failures' occurred more randomly.
Read/write heads actually float on a cushion of air created by the spinning of the disc. Older designs "loaded" the heads against the surfaces after the drive is spinning. Newer designs "park" the heads in a null spot until the drive starts up, but are always 'loaded'.
Ergo, starting and stopping the drive allows the head to land on the surface (wear on head) and exposes you to electronic failures due to power spikes.
BUT, constant spinning wears the spindle bearing assembly, and you can sometimes see (hear) this on older drives as they become noisier. The one advantage this choice offers is the likely-hood you will hear the increased noise and back up your drive before failure.
The greater concern in my mind, than either of these scenarios, is the constant scans performed by security programs which are 'pounding' drives relentlessly, day after day. The R/W heads are linked by tiny wires or film strips to circuits on the base. These electrical connections 'flex' with every repositioning. If you bend a conductor enough times---.
Not to be 'un-green', The power consumption issue would be offset by skipping one trip downtown a year. Probably for your whole PC if you live in a metropolitan area and wait in traffic! Roger

My "old" Maxtor drive, which was not even a year old, failed BECAUSE I turned it on and off every time the computer was shut down. The on/off switch failed, and I had to jiggle it to get it to run. My new drive, a W/D turns itself on and off with the computer, so there is at least no mechanical failure possible like there was with the Maxtor.

If you dont have a fast connection USB it will take ages to 'Boot Up' when you switch on if your xternal hard drive is in the on'' mode: correct?
LOVE YOUR NEWSLETTER. DOMENIC.

I have a Maxtor External hard drive and I've never seen it power-down. and I have left it turned on & unused for a long period of time. It also doesn't have an on/off switch for some reason.

I have three external drives, only the oldest a Freecom 120GB model has no switch and turns itself on and off with the computer. It was the first external drive I bought and contains DV video files I edit on Premiere so it is used either intensively, or not at all so the answer is to unplug the USB cable unless I specifically need it. Both the other drives have power switches.

In an ideal world with a multi-external drive setup we would be organised to have one set ot type of files on one drive (i.e. photos), another with a different type (office work, etc), and one for backups but the reality it it doesn't work that way as developing another arrow to my PC bow means I have hundreds of different filetypes.

Also, those handy personal external drives that work off USB power and now reach 160GB or more capacity will ALWAYS switch on and off with the PC/Laptop, so as these are more expensive in the first place are they economically viable with all that wear and tear bearing inmind the travelling wear and tear in a bag?

Keep up the good work, great site and newsletter!

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Domenic: not correct. The speed of your USB should only
affect your data transfer rate. The connection isn't used
that heavily when booting (if at all) - unless of course
you're booting *from* the USB device, in which case yes,
it'll be slower.

Leo

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My Maxtors (I have two) do not *power* down, but they do
*spin* down. Meaning that the lights stay on, but the drive
stops rotating. Biggest clue is that as soon as you browse
the drive beyond the root or current folder there's a 10-15
second delay as the drive spins up.

Leo

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I have a Maxtor external drive attached to my Mac and it doesn't seem to spin down. There is no delay when I browse three or four folders deep after it has been setting there for some time. The vibration level also seems to remain constant at all times. It should feel a bit different if there were just a fan running and not the drive.

One additional factor not mentioned was the role of power supply stability. Power surges from the AC line do not help, and brief interruptions (often due to lightning or bad weather) do not help the longevity of hard drives either. I use a ZeroSurge series filter plugged into the AC outlet to protect against surges, and a APC un-interruptible power supply plugged into the Zero Surge to protect against interruptions, with the PC of course being plugged into the APC.

To Roger: Not all drives use the CSS (contact start/stop) mechanism you described. All Hitachi hard drives use a load/unload ramp, which causes no friction wear to the head. (Ramps can have other issues, however.) Seagate's 3.5" drives still use CSS, last I heard, so people who use that vendor may wish to avoid excessive power cycling.

Also, most spindle bearings are FDB (fluid dynamic bearings) so bearing wear isn't nearly as much of an issue as it used to be. Modern flex tapes generally don't have fatigue issues, either, at least from what I hear being in development. (I work in the industry.)

Other remarks: What does concern me is electronics wear with power cycling, since electromigration effects are greater as transistor size shrinks (current generation SOCs are 90nm). However, risk of head-disk interaction as a result of internal contamination, application of external force, or other issues (firmware problems, failure to park on an emergency power-off, etc.) counterbalances the argument to leaving a drive on all the time, since usage of the drive raises risk of HDI. Excessive heat due to the drive running can exacerbate thermal decay of written data, as well.

All drives will experience degradation of the magnetics because of superparamagnetism, whether they are on or off. This is a practical limit on the lifespan of a drive due to degradation of the once-written servo pattern. Copying data to an HDD and leaving it in the closet for 5 years is NOT safe -- I'd prefer optical media. (Just make sure to use a high-quality brand like Taiyo Yuden, not the cheap stuff, which can delaminate.)

In the end, because of the complexity of HDDs, the differences in models, and the difficulty of extracting probabilities of failure, whether to power down or not is still a matter of preference. I shut off most all of my HDDs when not in use, since I view the mechanical and magnetic risks to be greater than the electronics ones. Thus far, I've had good luck. If one chooses to leave a drive on all the time, definitely make sure it's well cooled. Multiple backups over multiple drives is the safe thing to do. Also, don't trust what the manufacturer says about drive life -- the one oddball failure on the Weibull projection could be the one with your data on it.

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