Re: Speed Problem Copying Files

[David Christensen <dpchrist@holgerdanske.com>]

On 5/14/19 4:23 AM, Michael Stone wrote:
> On Thu, May 09, 2019 at 10:48:31PM -0700, David Christensen wrote:
> > 2019-05-09 22:00:27 root@po /mnt/scratch
> > # time dd if=/dev/urandom of=foo bs=1M count=1K conv=fsync
>
> don't bother doing this, urandom will be the bottleneck and it will just 
> confuse things

That was intended more as a litmus test, rather than a benchmark.  I 
chose /dev/urandom, rather than /dev/zero, to preclude the possibility 
of caches or compression.


The test succeeded in finding a disk write problem:

On 5/13/19 1:30 AM, Lothar Schilling wrote:
> # time dd if=/dev/urandom of=test bs=1M count=100 conv=fsync
> 100+0 Datensätze ein
> 100+0 Datensätze aus
> 104857600 Bytes (105 MB, 100 MiB) kopiert, 192,778 s, 544 kB/s
> real    3m12,781s
> user    0m0,000s
> sys     0m1,480s


David