DPM ftpd tcp nodelay

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DPM had a problem transferring effectively from a dCache SRM in versions prior to 1.4.4 (that is, LCG release 2.6.0 and earlier).

The workaround below should only be applied if you are still running one of these older DPMs.

In code which fixed this bug in DPM versions 1.4.4 and 1.4.5 relied on gethostbyname() returning the machine's fully qualified domain name. If your host does not, modify this by:

  • Setting the hostname to the FQDN using the hostname command:
 # hostname myhost.mydomain.ac.uk
  • Modifying the HOSTNAME= stanza of /etc/sysconfig/network to give the correct FQDN at boot time.

Or, you can apply the "old fix" below. (Though modifying the hostname is preferred.)

In theory it is possible to see slow transfers when using a gridftp server which does not physically host the required file, however, any transfers initiated via SRM will give a TURL matching the gridftp server to the file server, so it is not a problem in practice.

Early DPM Workaround (Versions < 1.4.4)

To ensure that DPM can transfer effectively from a dCache make sure the following option is set in /etc/sysconfig/dpm-gsiftp on the DPM head node and all the pools:

 # Fix for slow transfers from dCache sources
 export RFIO_TCP_NODELAY=yes

(Restart dpm-gsiftp after setting this.)

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