Re: Slow I/O on USB media

[Andrea Vai <andrea.vai@unipv.it>]

Il giorno mer, 05/06/2019 alle 19.39 +0200, Greg KH ha scritto:
> On Wed, Jun 05, 2019 at 06:23:58PM +0200, Andrea Vai wrote:
> [...]
> In ssh I manually mount the media,
> then
> > run
> > 
> > touch begin
> > date
> > <cp command>
> > date
> > touch end
> 
> That tests nothing other than the size of the memory in your system
> :(
> 
> You have to flush the data out to the device fully in order to
> properly
> measure device throughput.  Calling 'touch' does not do that.
> 
> > If I use the DE (where the media is mounted automatically) I used
> to
> > "eject" the media after the copy finished, and took note of the
> time
> > used until the media was correctly "ejected" (and, so, unmounted).
> 
> eject/unmount is good.
> 
> > Anyway, I know that I can do all of this in a better way, and will
> let
> > you know.
> 
> Yes, please do so, your steps above do not show much.

so, just to be sure now, here is my test script:

touch inizio
date
mount UUID="6a9d3c05-6758-49c0-a46e-6ce221478eb3" /mnt/pendrive
cp /NoBackup/buttare/ubuntu-14.04.5-desktop-i386.iso /mnt/pendrive
umount /mnt/pendrive
date
touch fine

can you please confirm (if) it's fine?

> 
> And you need to get your auto-mount out of the way, as who knows
> what
> options your device is being mounted with (i.e. sync or no
> sync).  You
> have to control that yourself in order to be sure.

yes, I disabled the auto-mount. Furthermore, is there any option I
need to specify to the mount command (i.e., as you say, sync or no
sync)?

thanks,
bye
Andrea