Synchronize clocks

Synchronize the clocks on all nodes and application servers.

Use Network Time Protocol (NTP) to synchronize the clocks on all nodes and application servers.

Synchronizing clocks is required because DataStax Enterprise (DSE) overwrites a column only if there is another version whose timestamp is more recent, which can happen when machines are in different locations.

DSE timestamps are encoded as microseconds because UNIX Epoch time does not include timezone information. The timestamp for all writes in DSE is Universal Time Coordinated (UTC). DataStax recommends converting to local time only when generating output to be read by humans.

  1. Install NTP for your operating system:
    Operating system Command
    Debian-based system
    sudo apt-get install ntpdate
    RHEL-based system1
    sudo yum install ntpdate 
    1On RHEL 7 and later, chrony is the default network time protocol daemon. The configuration file for chrony is located in /etc/chrony.conf on these systems.
  2. Start the NTP service on all nodes:
    sudo service ntp start -x
  3. Run the ntupdate command to synchronize clocks:
    sudo ntpdate
  4. Verify that your NTP configuration is working: