Paul Eggert wrote:
Pádraig Brady wrote:
The attached patch changes the output to:
$ dd if=/dev/zero of=/dev/null bs=256M count=2
2+0 records in
2+0 records out
536870912 bytes (512 MiB) copied, 0.152887 s, 3.3 GiB/s
I recall considering this when I added this kind of diagnostic to GNU
dd back in 2004, and going with powers-of-1000 abbreviations because
secondary storage devices are normally measured that way. For this
reason, I expect many users will prefer powers-of-1000 here. This is
particularly true for transfer rates: it's rare to see "GiB/s" in
real-world prose.
So it'd be unwise to make this change.
----
When users see 512 MB copied, they expect it means 512*1024*1024.
The same goes for the GB/s figure.
If you went with Gb/s -- that's different, as we are more used to seeing
bits/s, which
is why I could go either way with that.
The simplest thing to do is to leave "dd" alone, which is my mild
preference. Alternatively, we could make the proposed behavior
optional, with the default being the current behavior. If we do that,
though, the behavior shouldn't be affected by the abbreviation chosen
for the block size. Even if the block size is given in powers-of-1024
(which is common, because block sizes are about internal memory units,
where powers-of-1024 are typical), the total number of bytes
transferred and the transfer rates are more commonly interpreted in
the external world, where powers-of-1000 are typical.
----
What external world are you talking about? Where you talk about MB or
GB /s outside of the
computer world? If what you said was true, then people wouldn't have
responded that 125MB/s
was impossible (in the external world) on a 1Gb ethernet. Yet that's
what 'dd' displays.
See
"http://superuser.com/questions/753597/fastest-way-to-copy-1tb-safely-over-the-wire/753617";.
See the comments under the the 2nd answer. "125MB/s is literally
impossible with a 1Gbit/s line - there will be overhead..."-(Bob) and
"Without very significant compression (which is only achievable on
extremely low entropy data), you're never going to see 125 MB/s in any
direction on GbE." (allquixotic).
They don't believe 125MB/s is possible even though that's what 'dd'
stated. It never occurs to
people, talking about computers and speeds that someone has slipped in
decimal -- it never happened before disk manufacturers wanted to inflate
their figures. By not putting a stop
to the nonsense that MB != 1024*1024 when disk manufacturers muddied the
waters, it's led
to all sorts of miscommunications.
The industry leader in computing doesn't use KB to mean 1000B, nor
M=10^6 ... Microsoft's
disk space and rates both use 1024 based measurements.
So what external world (who's opinion matters in the computer world) are
you talking about?
