Logical vs. physical blocks on various media and how to detect
Peter Van Hove
peter at Smart-Projects.net
Tue Oct 11 09:58:24 PDT 2011
Formatted message: <a href="http://www.t10.org/cgi-bin/ac.pl?t=r&f=r1110110_f.htm">HTML-formatted message</a>
I know that on CD, a logical block is also a physical block. The error
detection and correction is done on that one block and if block x is
unreadable, blocks x-1 and x+1 may very well still be readable.
On DVD it is different. The logical block size is 2K but an actual
(physical) ECC block spans 16 of those logical blocks. Error detection and
correction is applied to the 32K ECC block rather than every logical 2K
If one logical 2K block is unreadable, then infact 16 of those are unreadable
as the entire ECC block is unreadable.
On Blu ray finally, the same principle but then 32 logical 2K blocks or a
physical block of 64 K.
I was wondering if I can apply the same logic on thumbdrives / SD cards, SSM,
Hard Drives etc.
I don't know however, if the same logic applies, how to get that information
|from a device, or is there a fixed number to be taken in account for every
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