If you use two Linux Servers with NFS Shares connect over Gigabit Interfaces for Backups, you perhaps remark performance problems on using rsync.
It does often pause transmissions or reach only a rate of 32Mb/s. That’s bad and waste time and energy.
Background:
After some Tests of running Backups with single files and compressed big archives, the scans of my tools like iftop, systat, iptraf found out that the used Option „rsync -avz“ was the bottle neck, cause the Data Rate break down at intervals. The „z“ compress option was described on howtos as must have for slower networks did not work like a „on the fly permanent transmission“. My two Test Servers use each 3 Gigabit bonded NIC Cards, if the rsync command compress the Files, they were first pulled to RAM Cache and compressed there later after a small pause send.
Solution:
If you disable and remove the „z“ option and on used bash scripts as „batch run“ removing the „v“ Option too, i was able to send Data at range of 133MB/s.
On fast Network do:
$rsync -a /source/ /nfs-mounted-destination