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I have a Samsung Spinpoint HM640JJ as secondary drive in my MacBook (so it is not my boot drive) for about 2.5 years now. In short, it is a 640 gb, 16 mb, 7200 rpm, sata 3 disk.

I have only used up 320Gb of the drive (and 275Gb is still free).

Since a couple of days it has become really slow (e.g. copying to the drive and unzipping to the drive), although access time is still normal.

OSX's disk utility program does not detect any problems and is not able to repair anything. When I do a read/write benchmark with 5Gb files (Black Magic diskspeed test) with a drive temperature of 33 degrees Ceclius, I get the following speeds:

  • read: 76.8 MB/s
  • write: 69.0 MB/s

That is way too low, is it not? Is this an indication that the drive is dying?

What more can I do to verify the disk's health?

Thanks, Vincent

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I don't thin slowing down is necessarily a symptom of a failing drive. How much of the drive is filled? Once it gets past 1/2 full there is an increased possibility of it slowing as you use more of it. – Xavierjazz Jul 22 '13 at 20:32
@Xavierjazz I thought that was only applicable to SSDs and not HDDs. – nc4pk Jul 22 '13 at 20:35
Thanks for the comment: I have only used up 320Gb of the drive (and 275Gb is still free). (I have added this information to my question) – Vincent Jul 22 '13 at 20:36
70-75 MB/s slow for a 7200 rpm disk? What are you comparing against? I just timed writing a 500 MiB file to my working drive (also 7200 rpm). Three times time ( dd if=/dev/zero of=zeroes bs=1048576 count=500 ; sync ; sync ) gave real time elapsed 0m8.254s, 7.954s, 8.373s, for a total write throughput of approximately 61 MiB/s (and note that due to the double sync, this includes physically writing the data to disk; writing to the cache was basically instantaneous, with dd reporting write times of just under a second all three times). – Michael Kjörling Jul 22 '13 at 20:46
up vote 2 down vote accepted

It could be a dying HDD, but you need to diagnose it a bit more than just speed. For example if you hear noises from your HDD, mostly "click"-sounds when it's reading/writing, then that's another pointer to a dying HDD.

Read/write speed depends on what you are writing to and what you are reading from. I would guess without having testing it, that it is normal to have a speed under 100MB/s, even if they support 300MB/s, most devices doesn't go up to that speed anyway.

You could try Hard Disk Sentinel, it should be one of the best (if not the best) tool out their to monitor, test, diagnose and even repair HDD's and SDD's.


It must be late as I didn't read about OS X and I don't think hdd sentinel works on Mac. And as i'm not a Mac user, then I don't know any alternatives, but i've tried to find some tools for you anyway.

This could be good read: The Top Five Mac Hard Drive, Diagnostic, and Repair Utilities

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