Infrastructure

Identifies certain software and settings that contribute to your node's infrastructure.

Network Time

To keep all cluster nodes time-synchronized, data-fabric requires software such as a Network Time Protocol (NTP) server (or chrony for RHEL 7) to be configured and running on every node. If server clocks in the cluster drift out of sync, serious problems will occur with certain data-fabric services. Data Fabric raises a Time Skew alarm on any out-of-sync nodes. For more information about obtaining and installing NTP, see http://www.ntp.org/.

Advanced: It is recommended to install an internal time server with which the cluster nodes can sync directly. If internet connectivity is lost, the time on the cluster nodes stays in sync. For more details, refer to the preceding documentation link for NTP

System Locale

Ensure that your system locale is set to en_us. For more information about setting the system locale, see this website.

Syslog

Syslog should be enabled on each node to preserve logs for killed processes or failed jobs. Modern versions such as syslog-ng and rsyslog are possible, making it more difficult to be sure that a syslog daemon is present. One of the following commands should suffice:

syslogd -v
service syslog status

rsyslogd -v
service rsyslog status

Default umask

To prevent significant installation problems, ensure that the default umask for the root user is set to 0022 on all data-fabric nodes in the cluster. You can change the umask setting in the /etc/profile file, or in the .cshrc or .login file. The root user must have a 0022 umask because the data-fabric admin user requires access to all files and directories under the /opt/mapr directory, even those initially created by root services.

ulimit

ulimit is a command that sets limits on a user's access to system-wide resources. Specifically, it provides control over the resources available to the shell and to processes started by it.

The mapr-warden script uses the ulimit command to set the maximum number of file descriptors (nofile) and processes (nproc) to 64000. Higher values are unlikely to result in an appreciable performance gain. Lower values, such as the default value of 1024, are likely to result in task failures.

Warning: The data-fabric recommended value is set automatically every time Warden is started.

Depending on your environment, you might want to set limits manually for service accounts used to run I/O-heavy operations rather than relying on Warden to set them automatically using ulimit.

PAM

Nodes that run the Control System can take advantage of Pluggable Authentication Modules (PAM) if found. Configuration files in the /etc/pam.d/ directory are typically provided for each standard Linux command. Data Fabric can use, but does not require, its own profile.

Security - SELinux, AppArmor

See SELinux Support.

TCP Retries

On each node, set TCP retries for net.ipv4.tcp_retries2 to 5 so that data-fabric can detect unreachable nodes with less latency.
Note: The installation automatically sets TCP retries for net.ipv4.tcp_syn_retries to 4 on each node.
  1. Edit the file /etc/sysctl.conf and add the following line:

    net.ipv4.tcp_retries2=5

  2. Save the file and run:

    sysctl -p

NFS

Disable the stock Linux NFS server on nodes that will run the data-fabric NFS server.

iptables/firewalld

Enabling iptables on a node can close ports that are used by data-fabric. If you enable iptables, make sure that required ports remain open. Check your current iptables rules by using the following command:

$ service iptables status

In CentOS 7, firewalld replaces iptables. To check your current iptables rules, use this command:

systemctl status firewalld
To ensure that the required ports are available, disable firewalld by using this command:
systemctl disable firewalld

Transparent Huge Pages (THP)

For data-intensive workloads, data-fabric recommends disabling the Transparent Huge Pages (THP) feature in the Linux kernel.

RHEL Example

$ echo never > /sys/kernel/mm/transparent_hugepage/enabled

CentOS 7 Example

echo never > /sys/kernel/mm/transparent_hugepage/enabled

Ubuntu Example

$ echo never > /sys/kernel/mm/transparent_hugepage/defrag

Automated Configuration

Some users find tools such as Ansible, Puppet, or Chef useful to configure each node in a cluster. Make sure, however, that any configuration tool does not reset changes made when data-fabric packages are later installed. Specifically, do not let automated configuration tools overwrite changes to the following files:

Parent topic: Preparing each Node