rsync is too often CPU-bound

Torsten Bronger bronger at
Tue May 21 02:20:20 MDT 2013


While rsync works perfectly if you have little bandwidth, it is
difficult to use in a fast trustworthy local network.  Firstly, you
have to switch off compression, encryption, and checksum
calculation.  This is easily possible, although it can be hard for
people to collect all options necessary for fast-network tuning.

However, the CPU performance I observed was devastating.
Transfering big files, the NFS server uses <10% CPU, while rsync
daemon uses >80%.  Why is this?

Really critical is this with an NAS with a slow CPU.  In my case, it
limits the transfer rate from 55 MByte/s (NFS) to 12 MByte/s

For me, it means that I use NFS for data transmission, and use rsync
only locally on the client computer with a much faster CPU.  But
this should not be necessary in my opinion.  I think that at least
for big files, CPU and bandwidth performance of rsync and NFS should
be the same.


Torsten Bronger    Jabber ID: torsten.bronger at

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