Re: [rdiff-backup-users] slow incrementals over ssh to localhost

[Randall Nortman]

On Thu, Mar 08, 2007 at 09:59:20AM -0600, Jeff Strunk wrote:
> 
> I just found that it takes 3 times longer to perform an incremental backup 
> via 
> ssh of the local machine than to perform the incremental backup directly.
[...]

It is most likely due to the CPU overhead of encrypting and decrypting
(and possibly compressing/uncompressing) byte of data that needs to be
"transferred".  In fact, ssh to localhost can be slower than ssh to
another on the local network, because the CPU load is split between
the two machines.  Given that rdiff-backup is a bit of a CPU hog on
its own, adding the compress/encrypt/decrypt/uncompress overhead is
likely to peg your CPU usage at 100%.  Check this while you're running
the backup to confirm.  You are either CPU-bound or I/O-bound, and I
suspect it's CPU.

-- 
Randall