maplevshoney
Level 1 (13 points)
Mac OS X

Q: 2012 Mini Second Internal Drive Slow

I just made a head scratching discovery on my Mac Mini (which I use as a media server) and I'm wondering if anyone can give me any perspective on this.  I decided to add a second 1tb drive for media storage earlier this year.  I used the iFixit tutorial and added the second drive without any problems.  (The second drive I added came out of my wife's 2014 iMac, which I swapped with an SSD.  So both drives are original drives from Apple.)

 

I also have a RAID5 enclosure that has been giving me performance issues, so I ran the Blackmagic Disk Speed Test to see what kind of speed I'm getting.  To put the results in context I also did a speed test on both internal drives.  Oddly enough I discovered that the drive I keep the media on (the one I yanked from my wife's iMac) is getting crazy low Read speeds.  It typically won't even reach 1MB/s, but sometimes it will creep up to 5MB/s, but never more.  The write speed is also slow, but a lot faster by comparison.

 

This makes no sense to me as I am able to watch 10GB movie files on this drive using VLC player without any issues.  In fact, I have never noticed any performance issues whatsoever.  Could the Blackmagic Disk Speed Test be wrong?  Incidentally, it is accurate for all of my other drives, and I have tested it on about 6 now.  Could it be the SATA cable I'm using?

 

And why if the read speed is so low am I not noticing performance issues when I watch movies?  Do movies play back at a slower rate than this- even 10GB blu-ray files?

 

Any thoughts and comments would be appreciated, thanks!

 

DiskSpeedTest.png

Mac mini, OS X El Capitan (10.11.1)

Posted on Dec 11, 2015 2:50 PM

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maplevshoney

Q: 2012 Mini Second Internal Drive Slow

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  • by lllaass,

    lllaass lllaass Dec 11, 2015 3:24 PM in response to maplevshoney
    Level 10 (189,435 points)
    Desktops
    Dec 11, 2015 3:24 PM in response to maplevshoney

    In System Profiler

    OS X: About System Information and System Profiler - Apple Support

    what is listed as the link speed and the negotiated link speed for the slow disk

  • by maplevshoney,

    maplevshoney maplevshoney Dec 11, 2015 3:29 PM in response to lllaass
    Level 1 (13 points)
    Mac OS X
    Dec 11, 2015 3:29 PM in response to lllaass

    Link speed is 6 Gigabit and negotiated link speed is 3 Gigabit

  • by lllaass,

    lllaass lllaass Dec 11, 2015 3:39 PM in response to maplevshoney
    Level 10 (189,435 points)
    Desktops
    Dec 11, 2015 3:39 PM in response to maplevshoney

    The negotiated peed should be 6 but that does not account for the very slow performance.

    Open Disk Utility and repair the that disk and not if any errors repaired. Also is the SMART status listed as Verified?

  • by maplevshoney,

    maplevshoney maplevshoney Dec 12, 2015 7:05 PM in response to lllaass
    Level 1 (13 points)
    Mac OS X
    Dec 12, 2015 7:05 PM in response to lllaass

    Yeah the negotiated speed for my system disk is 6, not sure why the second disk is 3.  But definitely should be faster write speeds.  Disk Utility finds nothing and SMART status is good.  I also have SoftRAID which does diagnostics and the disk checks out.

     

    I'm not sure why I didn't think to do this before but I just manually copied a file off the disk, timed it and did the math, and got a read speed of 60Mb/s, which is a lot faster than what the Blackmagic Disk Speed Test shows. 

     

    Apparently the Blackmagic software isn't working on this disk, that's the only logical conclusion I can draw here.  Curiously it does seem to accurately measure the speed of my other disks.  Very strange.  I did a search and it seems that no one else has mentioned Blackmagic not working accurately, which I find to be odd.  Maybe I'll email the company and see if they respond.