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M-Vault Directory Server: Reliability & Fault Tolerance

M-Vault provides a number of capabilities to provide high reliability in mission critical environments.

Transactional Database

M-Vault utilises a high-performance transactional database. This provides a high level of assurance that hardware, operating system or application software failures will not corrupt a directory server database. It also enables the establishment of an on-line back-up regime for a directory service that will support both simple-recovery and disaster-recovery scenarios.

Database Hot Backup

M-Vault includes tools for backup of the databases while the server is running, so the directory service can provide uninterrupted service.

Database Recovery

The underlying on-disk database is transactional. This means that in the event of a system-crash or hardware failure then the database is recoverable once the machine and disk database have been brought up again.

Replication for High Read Availablility

Data can be replicated using X.500 DISP (Directory Information Shadowing Protocol). This enables the various servers in a distributed directory to hold local copies of data held elsewhere. This ensures that data is available if one server in the network goes down, and is key to achieving very high availability for read and search operations.

Key features include:

  • Total and incremental updates.
  • Primary and secondary shadowing.
  • Supplier and consumer initiated shadowing.
  • Authentication of supplier and consumer.
  • Scheduled and on-change updates.
  • Flexible replication configuration.

Failover Clustering for Master Reliability

M-Vault uses a single master architecture, which is the best approach for most directory deployments. High availability for search and read can be provided by directory replication.

M-Vault supports fail-over clustering which provides high reliability for the master server by enabling use of two servers with a shared RAID disk. This gives resilience for both disk and server failure. Isode recommends the use of dual-ported disks for best master performance.

Clustering can be deployed over a SAN to give Off Site Hot Standby (Disaster Recovery). This requires a fast network link, so is usually constrained to relatively short distances.

Disaster Recovery

In order to provide for flexible disaster recovery, M-Vault enables the configuration of one or more mirror servers, which are exact clones of the master server. In normal operation, these servers operates as standard shadow servers, providing high read availability. In the event of master failure, one of the mirror servers will be promoted to act as the master. This gives a flexible disaster recovery approach, which can work over long distance. Further information is given in the white paper “M-Vault Failover and Disaster Recovery”.