Re: [gentoo-user] {OT} USB 3.0 hard drive speed test

[Volker Armin Hemmann]

Am Donnerstag 11 August 2011, 10:30:04 schrieb Mark Knecht:
> On Thu, Aug 11, 2011 at 10:12 AM, Grant <emailgrant@×××××.com> wrote:
> > 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


please read man hdparm

  -T     Perform timings of cache reads for benchmark and comparison purposes.  
For meaningful results,  this  operation
              should be repeated 2-3 times on an otherwise inactive system (no 
other active processes) with at least a couple
              of megabytes of free memory.  This displays the speed of reading 
directly from the Linux buffer  cache  without
              disk access.  This measurement is essentially an indication of 
the throughput of the processor, cache, and mem-
              ory of the system under test.


as you can see, those numbers have nothing to do with the transport.

And 80mb/sec for a harddisk is really, really good.

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#163933