14.1.1.1. Setting Up Your Operating System for DRBD

To set your Linux environment for using DRBD there are a number of system configuration steps that you must follow.

  • Make sure that the primary and secondary DRBD servers have the correct host name, and that the host names are unique. You can verify this by using the uname command:

    shell> uname -n
    drbd-one
    

    If the host name is not set correctly, edit the appropriate file (usually /etc/sysconfig/network, /etc/hostname, or /etc/conf.d/hostname) and set the name correctly.

  • Each DRBD node must have a unique IP address. Make sure that the IP address information is set correctly within the network configuration and that the host name and IP address has been set correctly within the /etc/hosts file.

  • Although you can rely on the DNS or NIS system for host resolving, in the event of a major network failure these services may not be available. If possible, add the IP address and host name of each DRBD node into the /etc/hosts file for each machine. This ensures that the node information can always be determined even if the DNS/NIS servers are unavailable.

  • As a general rule, the faster your network connection the better. Because the block device data is exchanged over the network, everything that is written to the local disk on the DRBD primary is also written to the network for distribution to the DRBD secondary.

    For tips on configuring a faster network connection see Section 14.1.3, “Optimizing Performance and Reliability”.

  • You must have a spare disk or disk partition that you can use as the physical storage location for the DRBD data that is replicated. You do not have to have a complete disk available, a partition on an existing disk is acceptable.

    If the disk is unpartitioned, partition the disk using fdisk, cfdisk or other partitioning solution. Do not create a file system on the new partition.

    Remember that you must have a physical disk available for the storage of the replicated information on each DRBD node. Ensure that the physical partition on the DRBD secondary is at least as big as the partitions on the DRBD primary node. Ideally the partitions that are used on each node should have identical sizes, although this is not strictly necessary.

  • If possible, upgrade your system to the latest available Linux kernel for your distribution. Once the kernel has been installed, you must reboot to make the kernel active. To use DRBD, you must also install the relevant kernel development and header files that are required for building kernel modules. Platform specification information for this is available later in this section.

Before you compile or install DRBD, you must make sure the following tools and files are in place:

  • Kernel header files

  • Kernel source files

  • GCC Compiler

  • glib 2

  • flex

Here are some operating system specific tips for setting up your installation:

  • Tips for Red Hat (including CentOS and Fedora):

    Use up2date or yum to update and install the latest kernel and kernel header files:

    root-shell> up2date kernel-smp-devel kernel-smp

    Reboot. If you are going to build DRBD from source, then update your system with the required development packages:

    root-shell> up2date glib-devel openssl-devel libgcrypt-devel glib2-devel \
    pkgconfig ncurses-devel rpm-build rpm-devel redhat-rpm-config gcc \
    gcc-c++ bison flex gnutls-devel lm_sensors-devel net-snmp-devel \
    python-devel bzip2-devel libselinux-devel perl-DBI

    If you are going to use the pre-built DRBD RPMs:

    root-shell> up2date gnutls lm_sensors net-snmp ncurses libgcrypt glib2 openssl glib
  • Tips for Debian, Ubuntu, Kubuntu:

    Use apt-get to install the kernel packages

    root-shell> apt-get install linux-headers linux-image-server

    If you are going to use the pre-built Debian packages for DRBD, you do not need any additional packages.

    If you want to build DRBD from source, use the following command to install the required components:

    root-shell> apt-get install devscripts flex bison build-essential \
    dpkg-dev kernel-package debconf-utils dpatch debhelper \
    libnet1-dev e2fslibs-dev libglib2.0-dev automake1.9 \
    libgnutls-dev libtool libltdl3 libltdl3-dev
  • Tips for Gentoo:

    Gentoo is a source based Linux distribution and therefore many of the source files and components that you need are either already installed or are installed automatically by emerge.

    To install DRBD 0.8.x, you must unmask the sys-cluster/drbd build by adding the following line to /etc/portage/package.keywords:

    sys-cluster/drbd ~x86
    sys-cluster/drbd-kernel ~x86

    To enable the DRBD kernel module, you must rebuild your kernel, although the method depends on the kernel version you are using. Determine your current kernel version using uname -a.

    • For Linux kernels lower than 2.6.33, enable the userspace kernelspace linker to build and load the DRBD kernel driver. To enable the kernelspace linker, rebuild the kernel with this option. The best way to do this is to use genkernel with the --menuconfig option to select the option and then rebuild the kernel. For example, at the command line as root:

      root-shell> genkernel --menuconfig all

      Then through the menu options, select Device Drivers, Connector - unified userspace <-> kernelspace linker and finally press 'y' or 'space' to select the Connector - unified userspace <-> kernelspace linker option. After you exit the menu configuration, the kernel is rebuilt and installed. If this is a new kernel, update your bootloader to point to the kernel if the kernel version is different than your current kernel version. Now reboot to enable the new kernel.

    • For Linux Kernel 2.6.33 and later, DRBD is included within the kernel sources. To enable the DRBD module you must rebuild your kernel. The best way to do this is to use genkernel with the --menuconfig option to select the option and then rebuild the kernel. For example, at the command line as root:

      root-shell> genkernel --menuconfig all

      Then through the menu options, select Device Drivers, Block Devices, and then DRBD Distributed Replicated Block Device support. After you exit the menu configuration, the kernel is rebuilt and installed. If this is a new kernel, update your bootloader to point to the kernel if the kernel version is different than your current kernel version. Now reboot to enable the new kernel.

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