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On Thu, Aug 11, 2011 at 11:27 AM, Grant <emailgrant@×××××.com> wrote: |
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>>> I'm testing this USB 3.0 bus-powered hard drive: |
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>>> |
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>>> http://www.amazon.com/gp/product/B0041OSQ9S |
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>>> |
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>>> and I get: |
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>>> |
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>>> # hdparm -tT /dev/sdb |
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>>> /dev/sdb: |
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>>> Timing cached reads: 8006 MB in 2.00 seconds = 4004.33 MB/sec |
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>>> Timing buffered disk reads: 252 MB in 3.01 seconds = 83.63 MB/sec |
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>>> |
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>>> # hdparm -tT /dev/sdb |
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>>> /dev/sdb: |
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>>> Timing cached reads: 8230 MB in 2.00 seconds = 4116.54 MB/sec |
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>>> Timing buffered disk reads: 252 MB in 3.02 seconds = 83.55 MB/sec |
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>>> |
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>>> # hdparm -tT /dev/sdb |
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>>> /dev/sdb: |
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>>> Timing cached reads: 8446 MB in 2.00 seconds = 4224.36 MB/sec |
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>>> Timing buffered disk reads: 230 MB in 3.02 seconds = 76.28 MB/sec |
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>>> |
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>>> Wikipedia says USB 3.0 has transmission speeds of up to 5 Gbit/s. |
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>>> Doesn't MB/sec denote mega*bytes* per second? |
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>>> |
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>>> - Grant |
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>> |
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>> 4000MB/s = 4Gb/s |
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> |
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> OK, I thought "B" designated bytes and "b" designated bits. So when |
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> you see something like MB/s or Mb/s there's no way to know if it's |
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> referring to megabits or megabytes? |
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> |
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> - Grant |
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|
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Nahh, I made a mistake there. 4000MB/S = 4GB/S - You are correct, at |
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least as far as I'm concerned. |
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|
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Of course Volker, the man with the answer to everything, just told you |
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that 80 mega-bit / second was a 'really, really good hard drive' so I |
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guess we all make mistakes. ;-) |
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|
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I was really trying to point out that you ARE getting 80% of the USB |
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3.0 spec in the first number which is the speed of communications |
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across the USB cable talking to the drive interface. Sustained storage |
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rates of the drive don't have anything to do with that though. That |
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depends on the drive in the case. |
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|
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Cheers, |
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Mark |