Text 16727, 33 rader
Skriven 2013-08-27 16:07:02 av Maurice Kinal (1:261/38.9)
  Kommentar till text 16724 av Alexey Vissarionov (2:5020/545)
Ärende: usb iso verification
============================
Hey Alexey!

 AV> can you be sure that flash is really 16 Gb and not, say, 8 or 4?

The first zeroing of the flash with dd tells the tale.  If it successfully
zeros all the reported blocks one can easily do the math - number of blocks *
512 bytes.  However that won't really tell you if all those blocks are good
since they could have been zero to start with.  If one wants to ensure that
then writing a random block to the flash and reading it back helps to discover
whether or not each block is indeed writable.  That can be done in a loop with
dd, and yes it takes a very long time.  Also e2fsprogs has a simular checking
routine so one could always use that instead.

On a day to day basis it isn't often that this needs to be done.  Unless you
are a commercial enterprise in the business of distributing prewritten flash
disks I doubt one would require more than dd.  Also I haven't benchmarked csdck
so I am not sure it is all that much faster/better than dd.  I promise the next
time I buy one I'll do that.

 AV> Yes, that's the main reason why I've written this PoS (piece of
 AV> source).

Understood.  There is much garbage out there and from what I've seen most of it
appears to come in the form of SD cards, although a neighbour bought a pack of
ten 1G usb sticks once that turned out to be of extremely poor quality once. 
In that case it wasn't size that was the issue.

Life is good,
Maurice

... that path is sharp as a razor's edge - Katha Upanishad
--- GNU bash, version 4.2.45(2)-release (x86_64-unknown-linux-gnu)
 * Origin: Pointy Stick Society - Ladysmith, BC Canada (1:261/38.9)