[Nottingham] scp on the go slow?

[Martin]

On 05/02/13 12:05, Jason Irwin wrote:
> On 05/02/13 10:23, Martin wrote:
>> Sounds like write amplification slowdown...
> Something is deffo going wonky - the SAMBA copy went the same way and I
> also noticed the PC became dog-slow.
> The USB is also NTFS formatted for compatibility, which might not be
> helping matters.

Duh... Is that a USB external hard-drive as opposed to a USB flash
memory stick?...

High fragmentation?

Anything bigger than the Microsoft killer 2GByte limit?

Too long a USB lead causing problems?

Or even the USB lead draped over the power adapter and suffering errors
due to electrical/magnetic noise pickup?


>> To test your network, scp to dest.host:/dev/null to see if the speed
>> stays up or not.
> This is chugged along quite happily at around 26MB/s, which is pretty
> much what I would expect.

So the network and source both seem ok.


> Curiously, using Dolphin to do the copy into my home folder ran at
> 9MiB/s, but an scp into home was at 26MB/s.  Which I find odd as I would
> have expected a straight SAMBA copy to be faster than scp.
> 
> Be interesting to see what happens when I copy from home to the USB.

All rather curious as Alice would say...

Is either of the source or destination systems CPU or IO bound?


Asynchronous NFS is usually by far the fastest. scp is fast if your CPUs
are faster than the network IO. I wonder if ncat might be the fastest of
all?...

Cheers,
Martin

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