[paramiko] scp not sftp

[Robey Pointer]

On 23 May 2007, at 10:57, Rafael Ugolini wrote:

> James Bardin wrote:
>>
>>> By the way, you should be able to change this line:
>>>
>>>      chan.sendall("%s" % ( f.read()))
>>>
>>> to this:
>>>
>>>      chan.sendall(f.read())
>>>
>>>
>>
>> of course you may also want to add some sort of buffer, maybe
>> something like:
>>
>> s = f.read(32768)
>> while s:
>>    chan.sendall(s)
>>    s = f.read(32768)
>>
>> Robey,
>>    Would you have an idea why I can get full 100Mb/s transfers with
>> scp, but only 50-70% of that with sftp?  What kind of extra work is
>> sftp doing?

It's almost certainly the round-trip latency.  SFTP tends to send-and- 
wait: it sends one chunk of a file, then waits for it to be  
acknowledged.  You can get around that by turning on prefetch or  
pipelining.


> Robey,
>
> If you want, i can make a patch for paramiko, and you can put scp
> compatible with ssh version 1.

That would be cool!

It probably wouldn't be compatible with SSH version 1, though.  SSH  
v1 uses a different transport protocol.  I guess what's happening is  
that it's using scp v1 over an SSH v2 transport.

robey