rsync performance degradation? Could be a windows issue?

[Marco Atzeri]

On 11/04/2016 18:57, Greg Freemyer wrote:
> On Thu, Mar 31, 2016 at 4:48 PM, Greg Freemyer <greg.freemyer@gmail.com> wrote:
>> All,
>>
>> I'm not sure this is on-topic, but at least I'm in cygwin when I
>> notice the below:
>>
>> I do a lot of large data transfers between USB drives.  Often I get
>> great speeds (70MB/sec or more).
>>
>> Sometimes it falls way off to closer to 20MB/sec with the same class
>> of hardware.
>>
>> I experienced the "slow" transfer speed today, so I thought I'd ask if
>> anyone knew a way to resolve it?
>
> I'm trying rsync of a bunch of large files again today.
>
> Initially I saw the same slow copy speed (about 20 MB/sec).  My
> destination was connected to a USB 3.1 port, but it seemed to be the
> bottleneck so I moved it to a USB 3 port (3.1 should be 2x the speed
> of 3.0, so it should not have been the bottleneck).
>
> After getting my throughput up above 50 MB/sec I notice in the windows
> "performance monitor" that my source disk is hitting 100% utilization,
> then a few seconds later my destination disk is.  And back and forth.
> It seems I'm only reading or writing for a few seconds, then
> alternating.
>
> I assume the issue is that too much data is being read / cached by
> rsync prior to it being written out so I'm getting no advantage of
> reading and writing in parallel.
>
> (I gather iostat isn't available for cygwin?)
>
> Is there some rsync (or cygwin) option / feature that would encourage
> parallel reading/writing?
>
> fyi: I did some linux testing with "dd" over the weekend and I hit 140
> MB/sec if I used a 100MB blocksize.  That was to / from the raw disk
> (/dev/sda => /dev/sdb).
>
> If I bumped my blocksize to 1GB for dd in linux, my throughput dropped
> to 70 MB/sec just as I see right now with rsync in cygwin.
>
> Thanks
> Greg
>


Is windows robocopy faster ?



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