Overview of Technologies

Overview of Technologies

Pervasive PSQL is compatible with numerous solutions that maximize uptime in physical and virtual environments. Such solutions continually evolve but can be classified generally as high availability, fault tolerance, and disaster recovery.

High Availability

The definition of “high availability” can differ depending on the software vendor that provides high availability solutions. In general, it refers to a systems design approach for a predictable baseline level of uptime, despite hardware failure, software failure, or required maintenance.

A common approach to ensure high availability in a physical environment is failover clustering. A common approach in a virtual machine (VM) environment is migration.

Failover Clustering

Pervasive PSQL is designed to function as a resource in a failover cluster environment in which only one server node at a time accesses the shared storage subsystem. If the primary node fails, a failover (or switch) to a secondary node occurs. Failover clustering allows a system to remain available while you perform software upgrades or hardware maintenance.

Pervasive PSQL is compatible with Microsoft Failover Cluster Services and with Linux Heartbeat. Refer to the documentation from those vendors for the specific manner in which they define and implement failover clustering. Pervasive PSQL Server is the recommended product if the failover cluster uses physical nodes. Pervasive PSQL Vx Server is recommended for clusters that use VM nodes.

See Failover Clustering.

In general terms, migration allows a running VM or application to be moved between different physical machines without disconnecting the client or application. The memory, storage, and network connectivity of the VM are typically migrated to the destination.

Pervasive PSQL Vx Server is compatible with the migration capability offered by Microsoft Hyper-V, VMware vSphere, and Citrix XenServer. As long as virtual MAC addresses and host names remain the same after the VMs are moved, PSQL Vx Server continues to operate normally. Refer to the documentation from those vendors for the specific manner in which they define and implement migration.

Fault Tolerance

While high availability aims for a predictable baseline level of uptime, fault tolerance is the uninterrupted operation of a system even after the failure of a component. Fault tolerance requires synchronized shared storage. In virtualized environments, the VM that fails must be on a different physical host from the VM that replaces it.

Fault tolerance can be achieved using just physical machines. However, virtual environments lend themselves so readily to maintaining virtual servers in lockstep with each other that exclusively physical environments are increasingly less common. Pervasive PSQL Server is compatible with fault tolerance capabilities in an exclusively physical environment.

For virtual environments, Pervasive PSQL Vx Server is compatible with the fault tolerance capability offered by VMware vSphere and Citrix XenServer. Refer to the documentation from those vendors for the specific manner in which they define and implement fault tolerance.

See Fault Tolerance.

Disaster Recovery

Disaster recovery involves duplicating computer operations after a catastrophe occurs and typically includes routine off-site data backup as well as a procedure for activating vital information systems in a new location.

Pervasive PSQL Vx Server is compatible with major hypervisors that support disaster recovery technology that initializes backup physical or virtual machines. As long as all virtual MAC addresses and host names remain the same after the VMs are moved, PSQL Vx Server continues to operate normally. This allows rapid server replacement and recovery time. Pervasive PSQL Server is compatible with major hypervisors that support disaster recovery technology on physical machines.

Refer to the documentation from the hypervisor vendors for the specific manner in which they define and implement disaster recovery.

Another offering for Pervasive PSQL to help with disaster recovery is Pervasive PSQL Insurance. Pervasive PSQL Insurance gives you a way to get back online right away to keep your business going until you can restore the original Pervasive PSQL licenses. Pervasive PSQL Insurance provides a 7-day temporary license that allows 3 separate uses and is available for Windows and Linux 32-bit or 64-bit environments. See www.pervasivedb.com for details.

See Disaster Recovery.

Hardware Requirements

For all of the technologies mentioned in this section, Pervasive Software recommends that you select servers, disk subsystems, and network components from the hardware compatibility list provided by the vendor. Pervasive Software follows this practice when testing compatibility with vendor’s products.