Several technologies that are commonly employed in IT environments, such as uninterruptible power supplies, solid state drives, rest buttons, and replication, impact the considerations discussed in this paper. It is important to be aware of these technologies when developing the best strategy for your situations.
An uninterruptible power supply (UPS) is designed to provide emergency power in case of a power failure. This can be helpful by providing enough time for the system to shut down properly after loss of power. If the UPS is able to communicate with the computer's operating system, it can signal a shutdown in this event. The operating system can begin closing applications in an orderly manner while powered by the UPS.
The operating system will typically flush is own cache to disk during shutdown. It may not cause the disk controller to flush its cache.
If the UPS signals a shutdown, and FairCom DB is properly configured, it should cleanly shut down in this situation. The UPS must be properly configured to safely shut down the computer and FairCom DB Server before the UPS battery fails.
Because a solid state drive (SSD) has no moving parts, it can provide excellent performance and longevity. Unfortunately, not all SSDs are designed to provide data integrity in case of power failure. Because of this, some SSDs may not offer recoverability.
Know your drive. It is important when choosing a solid state drive to read its specifications carefully. Pay particular attention to specifications that pertain to reliability and recoverability. In addition, run tests on the drive you have selected so you can observe first-hand their behavior in case of a power loss.
WARNING: It is important to understand the devices used in your system.
The power button and the reset button are not necessarily designed to shut down the system in an orderly manner. They may shut off the power or initiate a microprocessor reset without allowing any caches to flush, which can result in data corruption. It is always important to perform a proper system shutdown to ensure data integrity.
The use of replication can enter into considerations about data integrity because it can be used to create a synchronized copy of the data. Because of the high-performance of FairCom replication solutions, the synchronization is done in nearly real-time. If a catastrophic failure occurs on the main server, almost all data can be recovered from the replicated copy. There is, however, no guarantee that every transaction can be recovered from the replicated copy. Only completed transactions are replicated and there is some delay in propagating them to the replicated copy.
Replication is only available when transaction processing is used. It also requires a unique index.