[LAD] [OT] bash vs disk activity

[Paul Davis]

On Thu, 2007-10-11 at 11:52 +0700, Patrick Shirkey wrote:
> On Wed, 2007-10-10 at 06:37 -0400, Forest Bond wrote:
> > Hi,
> > 
> > On Wed, Oct 10, 2007 at 09:51:35AM +0700, Patrick Shirkey wrote:
> > > On Tue, 2007-10-09 at 09:16 -0400, Forest Bond wrote:
> > > > On Tue, Oct 09, 2007 at 01:11:38PM +0200, Lars Luthman wrote:
> > > > > Slightly-slower-hack: add the 'sync' option to whatever script or config
> > > > > file is used to mount the device (/etc/fstab, udev rules, KDE service
> > > > > menu etc). That way all writes will be synchronised automatically.
> > > > 
> > > > It sounds like this doesn't matter much for you, but keep in mind that -o
> > > > sync doesn't cause reads to be unbuffered, so don't go trying to benchmark
> > > > your flash devices that way!
> > > 
> > > Hmm, I need speed and accuracy. 
> > 
> > But only for writes, no?
> 
> For the purpose of this script I am happy with just write but I will be
> needing read in the near future.
> 
> FYI, I can connect 200 usb-storage devices to a dual cpu intel with 4 GB
> RAM and an extra pci-usb card on the same irq as the internal usb bus. 
> 
> Basically I am uploading content to a couple of hundred mp3/multi media
> players at the same time and this script is used by other people with
> less Linux knowledge than I so I'm trying to make the progress bar as
> accurate as possible. Otherwise there is a significant lag between when
> the progress bar says it is finished to when the transfer is actually
> finished. Speed is also a major issue here so I cannot use the sync
> option as that causes way too much delay compared to async.
> 
> Can anyone here shed a little more light on how to monitor the disk
> activity while transferring data?

if you use your own compiled code for the copy, you can open the
destination files with O_SYNC. from man 2 open:


      O_SYNC The file is opened for synchronous  I/O.  Any  write()s  on
the
              resulting  file  descriptor will block the calling process
until
              the data has been physically written to the underlying
hardware.
              See RESTRICTIONS below, though.

this avoids having the entire mount be done with the sync option.