Availability refers to the ability of the user community to access the system, whether to submit new work, update or alter existing work, or collect the results of previous work. If a user cannot access the system, it is said to be unavailable. Generally, the term downtime is used to refer to periods when a system is unavailable.
Business continuity planning (BCP) is “planning which identifies the organization's exposure to internal and external threats and synthesizes hard and soft assets to provide effective prevention and recovery for the organization, whilst maintaining competitive advantage and value system integrity”. It is also called Business continuity & Resiliency planning (BCRP). The logistical plan used in BCP is called a business continuity plan. The intended effect of BCP is to ensure business continuity, which is an ongoing state or methodology governing how business is conducted.
Netzary Infodynamics has a number of custom solutions for BCP, HA and BCRP depending on the application which you are seeking to keep alive.
Some of the projects we work very closely include
Remus for Xen High Availability
Remus provides transparent, comprehensive high availability to ordinary virtual machines running on the Xen virtual machine monitor. It does this by maintaining a completely up-to-date copy of a running VM on a backup server, which automatically activates if the primary server fails. Netzary has build custom Kernels and VMs for Remus along with management scripts.
OpenStack High Availability
OpenStack can currently meet such availability requirements for its own infrastructure services, meaning that an uptime of 99.99% is feasible for the OpenStack infrastructure. The technology is built on Corsync and Pacemaker.
DRBD refers to block devices designed as a building block to form high availability (HA) clusters. This is done by mirroring a whole block device via an assigned network.
Linux High Availability Project
The Linux-HA project maintains a set of building blocks for high availability cluster systems, including a cluster messaging layer, a huge number of resource agents for a variety of applications, and a plumbing library and error reporting toolkit.
Heartbeat is a daemon that provides cluster infrastructure (communication and membership) services to its clients. This allows clients to know about the presence (or disappearance!) of peer processes on other machines and to easily exchange messages with them.
In order to be useful to users, the Heartbeat daemon needs to be combined with a cluster resource manager (CRM) which has the task of starting and stopping the services (IP addresses, web servers, etc.) that cluster will make highly available. Pacemaker is the preferred cluster resource manager for clusters based on Heartbeat.
Netzary Mail Server HA
Our own home grown HA solution for Postfix and other *NIX mailservers.