Try :
USB -> HDD.

Please dont use an SSD.

You are not testing correctly.

On Wed, Apr 1, 2020 at 8:56 AM Ed Greshko <ed.greshko@greshko.com> wrote:
On 2020-04-01 09:14, Roger Heflin wrote:
> To have the issue it helps to have the reading disk be a quite a bit
> faster than the receiving disk that way the reading disk can easily
> get ahead and fill up the write cache faster than the reading disk can
> process it (it backs up into the writecache).
>
> So USB3.0 3.5-7200rpm or an SSD will easily overrun a standard laptop
> 5900 rpm 2.5" hard disk.

This was not done on a quiet system CPU wise, boinc jobs running.  But not much other I/O going on.

SDD--->USB-Flash

real    16m38.608s
user    0m1.416s
sys     3m37.379s

USB-Flash--->SDD

real    6m37.671s
user    0m0.662s
sys     1m4.984s

I then found an old laptop HDD in a USB 2.0 enclosure.  Reading from the SDD should be much faster
than writing to the HDD.

SDD--->HDD

real    30m53.407s
user    0m0.942s
sys     2m46.756s

HDD--->SDD

real    32m48.615s
user    0m0.896s
sys     1m9.483s

And, for completeness

SDD--->SDD

real    4m58.406s
user    0m0.517s
sys     1m8.402s

No issues at anytime with stability or slowdown in all cases.


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