Clarify between decimal bytes and binary bytes

Pat LaVarre p.lavarre at IEEE.org
Fri Jul 9 17:52:01 PDT 2010


* From the T10 Reflector (t10 at t10.org), posted by:
* Pat LaVarre <p.lavarre at ieee.org>
*
 > IDEMA ... is the reported capacity ...
The way I hear it, IDEMA tells us how many bytes should be counted by  
SBC READ CAPACITY for any given drive capacity X within the domain of  
their formulae. On the other hand, me googling a little then doesn't  
immediately dig up much confirmation ...
 > http://physics.nist.gov/cuu/Units/binary.html
 > overwhelming NEED to use the binary terms ? If not, then no problem
 > http://en.wikipedia.org/wiki/Binary_prefix
 > ...
 > don’t ... have to deal with something that is not used in our  
standards ...
 > exactly what it is you are proposing to un-confuse
 > looks like everything is clearly stated. So where is the problem?
 > ...
 > IDEMA formula ... JEDEC ... not a T10 or T13 problem
 > ...
 > uncompressed capacity rather that the presumed compressed capacity
 > ...
 > SAS-2 ... megabytes ... decimal ...
 > SSC-4 ... megabytes ... decimal ...
 > SPC-4 uses binary units in an EXTENDED COPY command-related	
TRANSFER COUNT field (see pg 324 table 206) ...
 > SES-3 uses binary units to report non-volatile cache sizes (see pg  
100 table 94) ...
 > SBC-3 uses binary units when discussing the addressing limits of  
READ(6) (see pg 99 note 10).  I thought we deleted ...
 > ...
 > See SPC-4 revision 25 section 3.6.4
 > SES-3 revision 2 section 7.3.11 table 95
 > SBC-3 revision 22 has no remaining uses of binary OR decimal  
prefixes, so no longer references IEC 60027.
 > ...
Also:
a)
That Nist.gov page works better when read aloud. Mebibyte sounds like  
may be byte, Gibibyte sounds like gibberish.
b)
Nist's best story is the "1.44 MB" unfloppy diskette that in fact held	
1.44 KKiB.
c)
Those IDEMA units are not simple linear translations. I once wrote on  
my cube wall:
1,000,194,048 B = 1 IDEMA GB circa 300 GB
I must have then been under the impression that the IDEMA unit for 1  
Gig has some other value at other capacities, courtesy their mystic  
formulae. It's not a simple relation like the more familiar:
1,000,000,000 B = 1 GB = 1 Gigabyte
1,073,741,824 B = 1 GiB = 1 Gibibyte
37+-5'C
98.6+-9'F
etc.
*
* For T10 Reflector information, send a message with
* 'info t10' (no quotes) in the message body to majordomo at t10.org



More information about the T10 mailing list