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Why Is There a Delay When I Try to Access My External Hard Disk?


I have an HP Envy 15 notebook PC running Windows 7. I have a 3 TB Western Digital external hard drive that I use for a backup drive. I do manual backups from my C: drive to it. I bring up the back-up directory on that hard drive and keep it inimized until I want to back up a file or directory (or a collection of those) to it. Frequently, when I click a directory on the backup drive, that window turns white and my cursor spins, causing an irritating delay in doing the backup. This must occur to other PC users as well. Do you know what causes that and what I can do to stop that from occurring?

It’s extremely common. I run into this all the time.

Even better – I’ll bet it only happens “sometimes.”

The problem isn’t really a problem, per se. It’s by design.

And we can’t even blame Windows.

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Sleepy Drives

Many external disk drives will “go to sleep” if they’ve not been accessed in a while.

This power-saving feature actually causes the hard disk to stop spinning, as that’s the single largest consumer of power in the drive. The circuitry in the drive stays mostly awake, awaiting a request to actually do something from your computer.

When that request comes in, the circuitry “wakes up” the drive. And like me before I’ve had my first cup of coffee … it takes a little time to wake up.

The problem is that the disk needs to “spin up” to full speed – typically 5000 RPM – before the external hard disk can act on whatever it’s been asked to do. Zero to 5000 take a couple of seconds.

A couple of seconds where your machine is waiting. Depending on the application being used and how it was written, those couple of seconds could cause the program to block completely until the drive is up to speed.

Annoying as that is.

Who’s to blame?

Well, to start with, it’s not a bug – it’s a feature. Drives that do this are attempting to save power by not spinning the hard disk when it’s not in use.

Unfortunately for many, if not most, this feature is simply built-in.

There’s no way to turn it off.

If you don’t use your drive at all for some period of time, usually around 10 minutes, the drive will go to sleep and turn off its hard disk.

Caching confuses

One of the reasons that this can often be confusing is that Windows will often cache the folder listing for whatever folder is current on that drive. If you plug in the drive and let it sit for 15 minutes so that it goes to sleep, you still might be able to see the contents of the top-level folder on the drive. Windows will have cached it from when the drive was inserted and doesn’t need the drive to spin up again to read what it already knows.

Do something else, however, like attempt to open a folder or copy a file to the drive and you’ll be faced with that multi-second delay as the drive wakes up and comes back up to speed before doing what you asked.

One work-around

If it’s really a problem, there is a work-around.

Access the drive every so often. If the drive times out at 10 minutes, then do something to the drive every nine minutes.

A folder read or directory listing won’t be enough, as Windows will have cached that. Even a file read could be cached.

Nope, you’ll have to do something slightly more serious.

Like write a small file to it every nine minutes. That can’t be cached and will keep the drive spinning and ready for you when you come along with some real work.

And that’s exactly what NoSleepHD does.

Caveat: I have not tested this utility; it’s just not something that I need. It appears like a simple solution that you can set up to keep your external drives from going to sleep.

But of course, as with all tools that you might download from the internet, use it  with caution, and of course, backup early and often.

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10 comments on “Why Is There a Delay When I Try to Access My External Hard Disk?”

  1. The disk spins down not only to save energy but to extend the life of the disk. Especially on portable disks that tend to run hot because they have no fan. So to avoid some inconvenience, you can be shortening the life of the disk.

  2. Unrelated issue is transfer speed.

    A 3TB drive is fairly new, and I’m willing to bet it comes with USB 3 support. USB 3 is up to 10 times faster than USB 2. For existing machines, you can by an add-in board to support USB 3 for around US$50.

  3. I found my Desktop Seagate 7200 RPM hard drives to consume about 100 Watts per hour when spinning. Here is what it cost to keep those spinning 8 hours a day if you you pay 12 cents per Killowatt hour for electricity:

    8 hours X $0.012 = $0.096 per day
    30 days X $.096 = $2.88 per month

    I cannot remember what I measured the pocket size hard drives to use but it was negligible compared to the full size drives.

    I keep my system on 24 hours a day and make sure none of my applications have to access external hard drives. My computer is a Lenovo Thinkpad Notebook that uses less than 65 Watts.
    It all can add up

  4. @John H. Normally a hard drive would take less than 10 W, but even with a power ticket of 10 W there would result an energy usage (in 8 hr) of 8 X 10 Wh a day. So that would be 0.080 kWh with a total cost of 0.080 X 12 = 0.96 cents per day and 28.8 cents per month. Or $ 3.50 per year. Not really alarming to the budget.

  5. Quick note… You say that writing to a file “can’t be cached”. That’s not true, as operating systems often cache writes to improve performance. (Multiple writes to the same disk location can be combined, for example, or the order of the writes can be rearranged for better throughput.) However, such caches are typically written to the physical drive relatively quickly, and you can often force the O/S to flush the cache immediately.

    Indeed. And I’d presume the little keep-alive program is telling Windows to flush the cache as well.

  6. Henk
    I was fairly specific in naming the hard drive I tested for power consumption. These are 3.5 inch 7200 RPM Drives. These are not portable mini hard rives or the ones used inside your laptop.

    I would assume the drives installed in tower or desktop computers consume large amounts of power but assumptions do not count, only real measurements.

    I used a Kilowatt brand power meter for the test. Again, these measurements are when the disk is spinning and not starting surge. When the disk is not spinning, power consumption is almost nil.

    It appears that there is a huge difference in power consumption between a 2.5 inch 500 RPM drive and a 3.5 inch 7200 RPM drive.

    Replacing your CRT monitor with an LED monitor would pay for itself if you keep your computer monitor on continuously.

    At times I live off the grid and am always looking at and measuring how I consume power.

  7. I feel that power consumption would be fairly minor compared with the wear and tear of having it running all the time, Especially when they are spinning at such high rpm.
    To have it running all the time would have to shorten the hard drive’s life!

    Actually, it’s unclear that this is the case. The act of starting up and slowing down, and heating and cooling, also “wears” on the drive. In many cases leaving the drive running continuously is actually easier on the drive. The one factor that someone mentioned earlier is interesting, though: since many portable drives often do not have fans it’s possible that they’re simply not designed to be left on continuously and their lives might be shorter due to overheating. Either way it’s not as simple “always running is bad for the drive”, since that’s not always the case.

  8. Control Panel > System > Hardware tab > Device Manager button > Select Drive > Properties by right click > Power Management tab > Uncheck “Allow the computer to turn off this device to save power”.

    I agree that it could be the hardware circuitry controlling the Sleep function but the above place is also worth looking. Maybe that could help.


  9. To stop it from going into sleep mode start any video in VLC media player, then pause and minimize. It will prevent sleep-mode.
    (let me know if this should be wrong plz.)

  10. The problem for me and many others is that it is a matter of 2 – 3 minutes before the external drive wakes up from the point you try to wright something on it. This is the way it works for me in Win 7. The same drive in XP wakes up in second after it has been tiold to wright something. This is all very annoying.


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