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I'm zeroing a drive with
dd if=/dev/zero of=/dev/sdd
on a USB 3.0 port and it appears that the disk is writing half of the time and reading half of the time.
17564 be/4 root 10.59 M/s 10.59 M/s 0.00 % 96.60 % dd if=/dev/zero of=/dev/sdd
The performance is slower than what I expect, only being ~10M/s write and it looks like the rest of the bandwidth is being taken up by reads. The disk is not mounted nor being used by any other program.
Is this expected with dd
?
I wonder if the
/dev/zero
input counts as a read. If you want to improve performance, using a buffer size would help, currently you are reading/writing a byte at a time:dd bs=1M if= of=
– Paul – 2016-12-05T05:51:24.4305Related? – Kamil Maciorowski – 2016-12-05T06:02:20.000
It appears that using bs and a count does just writes. Maybe without a count dd reads the disk in between writes to see if it is at the end. Kamil, that is exactly it, thanks! – Ric Clark – 2016-12-05T06:28:55.063
1I hope somebody provides a definitive answer to what is asked in the title, because I can't find actual documentation as to whether or not dd performs any verification of what it writes. – fixer1234 – 2016-12-06T01:06:54.057