[lug] ssh compression

[John Hernandez]

For your particular issue, another potential benefit of the rsync (over 
ssh -C) solution would be rsync's --bwlimit=KB/s option.

Peter Hutnick wrote:

> On Wednesday 01 May 2002 10:04 am, Hugh Brown wrote:
> 
>>I am doing an over the net backup of a mail server over an ssh tunnel.
>>The bandwidth that it is consuming is killing me.  Is there any way to
>>throttle it down?  Would using the compression option in ssh help me or
>>hurt me (the man page says it would slow it down, but I don't know if
>>that means less bandwidth, longer download or same bandwidth, longer
>>download).
>>
> 
> Sure, use compression (ssh -C or scp -C).
> 
> If I read you correctly, your main gripe seems to be that the transfer hogs 
> the entire connection.  I have wished for a long time that there was a 
> "netnice" command, so I could do things like "netnice -n 19 scp -C 
> someuser at somehost:~/somefile ."
 
<SNIP>

 
> But what you /really/ ought to do is use rsync, and use ssh -C as your 
> transport.  rsync is practically made for mailspools.
> 
> To summarize what rsync does, it treats all files as binary, breaks them into 
> chunks, does a hash against each chunk on both ends of the connection, then 
> sends chunks that are different.  So, instead of sending that entire 10M 
> mailspool each time you back up, it sends the last five 10k chunks to cover 
> the 47k of new mail.  Nice.
> 


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