[GRLUG] External drive transfer rates

[Justin Denick]

On 11/6/07, Bob Kline <bob.kline at gmail.com> wrote:
>
> Both the internal drive and the
> one hanging off the USB 2 cable
> are IDE.
>
> When I run the backup,  the
> machine is doing little else, so I'd
> guess the CPU is not particularly
> loaded.
>
> I'm a little puzzled as to why the
> hdparm  "d" parameter does not
> function,  but  the write says hdparm
> does not work with all chip sets.


I tried setting DMA on one of my IDE drives connected via usb
and I got the same error message.
The kernel doesn't see it as a PATA drive but rather SATA.

Well,  for now the backups work.
> I just have to wait.  The transfer
> rate is the 8 Mbps I mentioned.  Yet
> on another USB 2 port I can move
> data between two machines over
> a wireless link at 45 to 50 Mbps.
>
> So I think there is a mystery here
> yet.   I'd like to see at least that when
> backing up to an external drive on
> a USB 2 port.
>
> Someday...
>
>     -Bob
>
>
> > > hdparm -cuda  /dev/x
> > >
> >
> > I  forgot about one thing Bob.
> > hdparm only works for IDE drives, since your drive is interfaced via USB
> > it must be /dev/s-something right?
> >
> > if that it the case than DMA shouldn't be needed at all.
> >
> > As the purpose of DMA is to free up the processor maybe you should watch
> > the Load Avg when copying a file to see if it's
> > abnormally high.
> >
> >
> > only reports for a:  "readahead =  256 (on)
> > >
> > > Running   "hdparm -d1 /dev/x"
> > > result in "HDIO_SET_DEM failed: Invalid argument."
> > >
> > > The hdparm man page suggest that
> > > in rare cases one has to use the -X
> > > parameter.  It also says this can cause
> > > real headaches.
> > >
> > >     -Bob
> > >
> > >
> > >
> > >
> > >
>
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