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Full Discussion: DD command using block device as input
Special Forums Hardware DD command using block device as input Post 302667079 by Corona688 on Thursday 5th of July 2012 03:05:43 PM
Old 07-05-2012
Quote:
Originally Posted by nytty
At the application level page size is an important concept, it's the unit of interaction with the disk.
Agreed.

However, you're not actually interacting with the raw disk in your tests. You're telling the OS to do so for you, which does as it pleases. It will turn a tiny read into a much larger read for you -- ruining your results.

Even the OS isn't dealing with the disk raw, here. The OS asks the disk and the disk does what it pleases, pulling things from its own cache -- ruining your results.

Not to mention, you're running huge programs to do tiny things, which drowns your numbers in meaningless noise -- ruining your results.

Too bad there's not a program that actually deals with disks the way you want already... Something which can tell you transfer rates, bus modes, and bus speeds. Something which can configure software and hardware read-ahead, flush hardware caches at will, and all that jazz, letting you compare results for different configurations. Something which you can actually tell 'read raw sector x', and it will do so.

They really ought to make a program like that.

I bet they'd call it hdparm.
Last edited by Corona688; 07-05-2012 at 04:21 PM..
 

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LEARN ABOUT CENTOS

gnome-disks

GNOME-DISKS(1)							gnome-disk-utility						    GNOME-DISKS(1)

NAME

       gnome-disks - the GNOME Disks application

SYNOPSIS

       gnome-disks [OPTIONS]

DESCRIPTION

       gnome-disks is the command to launch the GNOME Disks application. Disks provides a way to inspect, format, partition and configure disks
       and block devices.

       The Disks application is single-instance. What this means is that if the application is not already running when the gnome-disks command is
       invoked, it will get launched and the command invocation will block until the application exits. Otherwise the existing application
       instance will be used and the gnome-disks command will exit immediately.

OPTIONS

       The following options are understood:

       --block-device DEVICE
	   Switches to the Disks application and selects the block device given by DEVICE (for example, /dev/sda).

       --block-device DEVICE --format-device [--xid WINDOW-ID]
	   Shows the "Format Volume" dialog for the block device given by DEVICE (for example, /dev/sdb1). If WINDOW-ID is given, makes the dialog
	   transient to the given XID.

       --help
	   Prints a short help text and exits.

AUTHOR

       Written by David Zeuthen <zeuthen@gmail.com> with a lot of help from many others.

BUGS

       Please send bug reports to either the distribution bug tracker or the upstream bug tracker at
       https://bugzilla.gnome.org/enter_bug.cgi?product=gnome-disk-utility.

SEE ALSO

       gnome-disk-image-mounter(1), udisks(8)

GNOME
								    March 2013							    GNOME-DISKS(1)
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