HA (High Availability)

This service is packaged inside nethserver-ha RPM.

The only supported scenario is a two node cluster in active-passive mode.

This package configures:

  • a DRBD storage in Primary/Secondary mode, the block device is formatted using ext4 and is mounted only on master node
  • Corosync and pacemaker
  • A virtual IP on green interface

Architecture

Components:

  • clustering is done using pacemaker and corosync
  • configuration tools are pcs and ccs
  • service data are stored inside a DRBD storage

Constraints

  • DRBD resource is named drbd00
  • System names are fixed: ns1 for primary node, ns2 for secondary node

Database

The ha key is saved inside the configuration database and should be the same on both nodes.

Available options:

  • ClusterName: cluster name used for Corosync, if blank a hash of virtual the virtual IP will be used
  • DrbdDisk: device where DRBD is stored, default is /dev/VolGroup/lv_drbd
  • VirtualIP: virtual ip for clustered services
  • VirtualMask: virtual netmask for clustered services, default is 255.255.255.0

STONITH and resource fencing

The cluster mys t be configured for both STONITH and resource fencing. Resource fencing is already configured at DRBD level using Corosync Redundant Ring Protocol.

STONITH fencing must be set using pcs command line tool.