- High-availability file system support

# High-availability file system support

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Intel® Manager for Lustre* software includes several capabilities for configuring and managing highly-available Lustre* file systems.

Generally, high availability (HA) means that the file system is able to tolerate server hardware failure without loss of service. The key components of this solution are the software components Corosync and Pacemaker. Corosync is responsible for maintaining intra-cluster control and heartbeat communications, and Pacemaker is responsible for managing HA resources (e.g., Lustre* targets).

To support automatic server failover, each HA server must have a dedicated crossover connection to the other server that will be its HA peer. During file system creation, each HA server is designated as a primary server for one or more targets, and as a failover, peer server for its peer server's targets. This crossover connection is configured as a redundant Corosync communications interface in order to reduce the likelihood of false failover events. Intel® Manager for Lustre* software uses a managed server profile to automatically configure Corosync and Pacemaker. The managed server profile is used to configure primary and failover servers. See the following figure.

Physically, HA peer servers must be cabled to provide equal access to the pool of storage targets allocated to those peers. For example: server 1 and server 2 are cabled as HA peers. Targets A and B have been configured with server 1 as their primary server and server 2 as their failover server. Targets C and D have been configured with server 2 as their primary server and server 1 as their failover server. If server 1 becomes unavailable, server 2 must have access to the block storage devices underlying targets A and B in order to mount them and make them available to Lustre clients. The end result is that server 1 is powered off and server 2 is now exporting targets A, B, C, and D to Lustre clients.

To support HA failover, each HA server must be able to automatically power-off its peer server if a failover is required. The process of powering off a faulty server is known as "node fencing" (also called "server fencing"), and ensures that a shared storage device is not mounted by more than one server at a time. Lustre includes protection against multiple simultaneous device mounts, but automatically powering off the faulty server ensures that failover works properly. Intel® Manager for Lustre* software supports the use of remotely-operable Power Distribution Units (PDUs) for this purpose. Alternative to the configuration of PDUs, Intel® Manager for Lustre* software also supports the Intelligent Management Platform Interface (IPMI) and associating baseboard management controllers (BMCs) with servers, to support server monitoring and control.

Note: See the Intel® Manager for Lustre* Partner Installation Guide for physical design and configuration guidelines required to support high availability.