[mdlug] External Hard Drives: Mounting, Unmounting, Partial Mounting?

[Aaron Kulkis]

Elisa Gomez wrote:
> First, sorry I've missed the last two meetings!
> Hopefully you'll see my shining happy face again in
> February.
> 
> Second, I am having all sorts of difficulty with this
> usb external hard drive that my mom just gifted me
> with. First, I want to say that I don't want to run
> another OS on here and boot into this occasionally or
> do anything fancy unless it's necessary to get this to
> work properly -- I just want to be able to save/back
> up data to the external drive . . . Kind of like if I
> had a folder on my desktop that magically had 320gigs
> of space in it.
> 
> But for whatever reason, Ubuntu (Gutsy) seems to only
> be partially recognizing the drive. I've labelled it
> (msdos) and formatted it (ext2) with gparted. At
> least, I *think* I have. It shows up in gparted as
> /dev/sdb as a seperate item without a mountpoint and
> this is what I get when I run df -k in terminal:
> 
> Filesystem           1K-blocks      Used Available
> Use% Mounted on
> /dev/sda2             16468952   8821640   6810728 
> 57% /
> varrun                  513208       148    513060  
> 1% /var/run
> varlock                 513208         0    513208  
> 0% /var/lock
> udev                    513208        84    513124  
> 1% /dev
> devshm                  513208         0    513208  
> 0% /dev/shm
> lrm                     513208     34696    478512  
> 7% /lib/modules/2.6.22-14-generic/volatile
> /dev/sda1             41094232  25192552  15901680 
> 62% /media/IBM_PRELOAD
> 
> So it doesn't actually seem to be there. Or am I
> misreading the output? It also doesn't show up
> graphically anywhere, as a desktop icon, as an option
> in the Places menu, etc. I can't save to it if I
> create a new file and Save As. Also, in gparted, the
> drive is showing up as 298gigs instead of 320gigs,
> which makes me feel like something windows related is
> installed on there.

Nope... it has more to do with the fact that disk drive
makers follow "the letter of the law" rather than the spirit
when it comes to marking the sizes of their products.

Hard drives sizes are measured in decimal kB/MB/GB/TB etc.,

But software reports in 2^10-based kB/MB/GB/TB/PB,
Which at the Gigabyte level, are 7% larger, so now


For clarity, the official 2^10 based units are now
designated as kiB/MiB/GiB/TiB/PiB

1 k = 1 000			1 ki = 1 024
1 M = 1 000 000			1 Mi = 1 048 576
1 G = 1 000 000 000		1 Gi = 1 073 741 824
1 T = 1 000 000 000 000		1 Ti = 1 099 511 627 776
1 P = 1 000 000 000 000 000	1 Pi = 1 125 899 906 842 624

So, the (software) 298 GiB is about = 319 975 063 552 Bytes,
which is within 0.3% of the (hardware) 320 GB.

On a related note, when looking at network bandwidth,
to find bytes/second, divide by 10, not 8.

100 Mbit/second ethernet will NOT give you ftp speeds
at 12 Mbytes/second... but instead, max out near
10 Mbyte/second, due to network overhead (both the
overhead of the Ethernet frames (transport layer)
and the TCP/IP frames (protocol layer), means that
for about every, say 800 bits of data that the programmer
sees, there's another 200 bits of Ethernet framing
and TCP/IP framing.