>>>> I'm testing this USB 3.0 bus-powered hard drive: >>>> >>>> http://www.amazon.com/gp/product/B0041OSQ9S >>>> >>>> and I get: >>>> >>>> # hdparm -tT /dev/sdb >>>> /dev/sdb: >>>> Timing cached reads: 8006 MB in 2.00 seconds = 4004.33 MB/sec >>>> Timing buffered disk reads: 252 MB in 3.01 seconds = 83.63 MB/sec >>>> >>>> # hdparm -tT /dev/sdb >>>> /dev/sdb: >>>> Timing cached reads: 8230 MB in 2.00 seconds = 4116.54 MB/sec >>>> Timing buffered disk reads: 252 MB in 3.02 seconds = 83.55 MB/sec >>>> >>>> # hdparm -tT /dev/sdb >>>> /dev/sdb: >>>> Timing cached reads: 8446 MB in 2.00 seconds = 4224.36 MB/sec >>>> Timing buffered disk reads: 230 MB in 3.02 seconds = 76.28 MB/sec >>>> >>>> Wikipedia says USB 3.0 has transmission speeds of up to 5 Gbit/s. >>>> Doesn't MB/sec denote mega*bytes* per second? >>>> >>>> - Grant >>> >>> 4000MB/s = 4Gb/s >> >> OK, I thought "B" designated bytes and "b" designated bits. So when >> you see something like MB/s or Mb/s there's no way to know if it's >> referring to megabits or megabytes? >> >> - Grant > > Nahh, I made a mistake there. 4000MB/S = 4GB/S - You are correct, at > least as far as I'm concerned. > > Of course Volker, the man with the answer to everything, just told you > that 80 mega-bit / second was a 'really, really good hard drive' so I > guess we all make mistakes. ;-) > > I was really trying to point out that you ARE getting 80% of the USB > 3.0 spec in the first number which is the speed of communications > across the USB cable talking to the drive interface. Sustained storage
As Volker pointed out, I don't think hdparm -T interacts with the USB system at all. I get the same rates whether the USB hard drive is plugged into a 3.0 port or 2.0 port. - Grant > rates of the drive don't have anything to do with that though. That > depends on the drive in the case. > > Cheers, > Mark
