rsync writefd_unbuffered failed to write error

[acoza]

looks like server is denying the write request. check if the remote file system is in good condition and there is no active firewall that block the connection.
Also make sure there is enough ram on both side to handle the rsync process

The sender has an Atom D520 2GB RAM. Receiver has X5620 24GB RAM. I think the receriver's file system is good as it just received a fresh OS install.

I do not use a firewall on the server level, but the DC does have a network wide firewall to guard against DDoS. Do you think this could be it?