Neverfail offers a High Availability & Disaster Recovery solution focused on continuous availability. To ensure continuous availability, Neverfail uses fully redundant servers including a Primary server and the Secondary server. Each server is capable of taking an active role or a passive role when servicing clients.
The servers can switch roles when the active server suffers any type of disruption or when you choose to do so manually, for any reason. Neverfail Continuity Engine monitors all the key components of the operations environment and can take action to correct a problem before users experience any type of outage.
At the completion of this session, you should be able to:
- Identify specifics about Neverfail Continuity Engine's Failover feature.
- Recall specifics about Neverfail Continuity Engine's Switchover feature.
- Identify how data replication and data roll-back work.
- Recall details of Neverfail Continuity Engine monitoring system, including hardware/system, network performance and applications.
- Select why Neverfail Continuity Engine protects auxiliary applications.
- Recall what you should do before implementing a LAN solution.
Key Features and Benefits
Failover vs. Switchover
Neverfail Continuity Engine uses two processes to change the server role from active to passive and vice versa. These processes can be set to occur automatically or can be initiated manually. Neverfail calls one a Failover and the other the Switchover. Users should detect no service disruption when either occurs.
Continuity Engine initiates a Failover when a hardware failure, power outage or similar condition causes the active server to fail critically. With the active server unavailable, the Failover process changes the passive server to the active role. The new active server immediately begins servicing clients.
The Switchover gracefully swaps the roles of the two servers. The active server becomes passive and the passive server becomes active. Continuity Engine initiates a Switchover when a less critical issue occurs, such as networking, applications or performance problems. You can initiate a Switchover manually when desired.
Switchovers are quick and seamless to end users, used to perform certain types of maintenance on your primary server, without any outage to the end user. All one would need to do is Switchover to the secondary server, perform your maintenance on the primary and then switch back, outage free. Keep in mind, certain types of maintenance affect the application data and application environment itself, such as application service packs and upgrades. Therefore, the switchover approach may not be appropriate in all situations. You can find additional information on this topic in the Neverfail knowledge base.
Continuous availability architecture
Due to Neverfail Continuity Engine's unique cloned server architecture, all Failover and Switchover operations are seamless to the end user.
During a Failover or Switchover users don't normally need to:
- Restart any applications.
- Log out log into windows.
- Make any configuration changes.
Other benefits for the I.T. operations environment include the following:
- Continuity Engine Switchovers and Failovers require no changes to active directory (AD).
- Consequently, it carries considerably less risk than solutions that do require these types of changes. The simpler the process, the more likely it is to succeed.
- Because changes to active directory are not required, Continuity Engine doesn't need to wait for AD replication before completing a Failover or Switchover, therefore you can typically complete Continuity Engine Failovers and Switchovers in a matter of seconds.
Neverfail Continuity Engine keeps the active and passive servers synchronized in near real time through the use of a proprietary replication engine. Continuity Engine replicates data changes at the byte level, only changing data, file and registry updates from protected applications.
Continuity Engine intercepts data changes on the active server and replicates them to the passive. Each server, however, may write data to disk asynchronously. This eliminates any potential performance impacts on the active or production server.
Benefits to Neverfail Continuity Engine approach to data replication include the following:
- The process is efficient because Continuity Engine replicates only changed data at the byte level.
- The active and passive servers remain in sync at all times.
- Because Continuity Engine replicates both file and registry updates from protected applications, even configuration changes to the protected applications are synchronized.
- And consequently, no manual intervention is required on the secondary server if the configuration of the primary server ever changes.
Data roll back
With all replication technologies, if data corruption occurs on the source server the corruption replicates to the target server. Neverfail developed the Data Rollback module to handle this situation if it occurs when Neverfail Continuity Engine is installed.
Admins can configure the Data Rollback module to take snapshots of the protected data at set intervals or on demand. If corruption occurs, you can roll the application back to a pre corrupted state.
As with replication, the Data Rollback module protects both the data on the disk, (as well as the registry), so that the application state remains consistent with its data. Some other data protection technologies protect the data only. By rewinding only the application data, they risk leaving the application in an inconsistent state. Continuity Engine rewinds both registry and application data.
Neverfail Continuity Engine provide several types of continuous monitoring:
- Hardware and system monitoring.
- Network monitoring.
- Performance monitoring.
- Application monitoring and protection.
Hardware and system monitoring
Continuity Engine continuously monitors the active server to ensure it's still working and available. Continuity Engine does so by sending a heartbeat message from the passive to the active. The message is more than a simple ping, as a crashed system with a functional network card can still respond to a ping even if the server is blue screened. The heartbeat message asks “are you alive?” to which the active server must respond “yes, I am”.
If the active server fails to respond within the allotted time, Continuity Engine can notify a system administrator and optionally perform an automatic Failover.
Neverfail Continuity Engine also can monitor of up to three IP addresses elsewhere on the network to ensure that:
- The server is still connected to the network.
- The network is still visible.
If the active server can't successfully contact all 3 IP addresses suggesting the network is down, Continuity Engine can initiate an automatic Switchover.
An important aspect of the Neverfail Continuity Engine monitoring system is performance monitoring, which takes the actions listed below:
- Continuity Engine monitors key performance attributes of the protected applications as well as a server hardware.
- You can configure Continuity Engine to take preemptive action to fix the problem such as restarting the service or running any predefined set of commands, if monitoring notices any performance problems or bottlenecks.
- If it can't correct the problem, an automatic Switchover can be initiated.
Application monitoring and protection
Neverfail Continuity Engine monitors and protects applications such as exchange or sequel server through use of Continuity Engine Plug-ins. Specifically, Continuity Engine monitors the state of the protected application. If monitoring detects the application services are not running, Continuity Engine can take preemptive action to fix the problem (such as restarting the service or running any predefined set of commands).
If Continuity Engine can't fix the problem, it can initiate an automatic Switchover.
High Availability and Disaster Recovery Protection
LAN network environments are ideally suited for high availability purposes due to the abundance of available bandwidth. Bandwidth in excess of 100 megabits allows the transfer of data to the passive server at nearly the same rate that the active server generates it. Since Neverfail Continuity Engine replicates data to any server located anywhere, users can achieve Disaster Recovery protection by placing the secondary server at an off-site facility and replicating the data through a WAN connection.
Continuity Engine has an optional WAN acceleration capability available for deployments with limited bandwidth. WAN acceleration provides data compression to reduce bandwidth needs. It also optimizes replication using deduplication, making the process ideally suited for low bandwidth connection.
In addition to the features described above, Continuity Engine also provides the following additional features:
IT administrators will often want alerts to problems or Failovers as they're occurring. Continuity Engine provides the ability to send an alert by way of:
- email (via any SMTP server)
- any other command line means (for example a net send message or a pager).
Protection of auxiliary applications
Continuity Engine Plug-ins provide protection for your business-critical applications. Usually business-critical servers are also running auxiliary supporting software on them as well, such as anti-virus programs and archiving programs. Continuity Engine protects these applications through the use of plugins for the following reasons:
- If you ignore the auxiliary application running on the server your primary application may not operate correctly.
- In order to provide true HA, you need to protect the entire environment including auxiliary applications.
Neverfail offers Plug-ins out of the box, requiring no custom scripting.
In this first course, we discussed the features and benefits of Neverfail Continuity Engine.
While Switchover is the graceful transition of application service, monitoring and control to the passive server, Failover is a similar transition resulting from the critical failure of hardware or the channel. During a Failover or Switchover, clients remain continuously connected, because all processes are seamless to the end user.
The Data Replication process transmits changed data, files and registry settings, from the active to the passive server via the Continuity Engine Channel.
Administrators can Rollback the entire state of an application to a prior point in time, with Continuity Engine Data Rollback module.
Hardware and system monitoring ensure that the active server is functional. Network monitoring ensures the active servers’ ability to communicate with the rest of the network. Continuity Engine monitors key performance attributes of protected applications and takes predetermined action to fix the problem.
Neverfail Continuity Engine sends email alerts and protects auxiliary applications through the use of Neverfail Plug-ins.
Continuity Engine provides true High Availability over a LAN and Disaster Recovery over a WAN.