Reliability holds immense importance in a robust database system, and PostgreSQL is fully dedicated to ensuring a dependable operation. In this blog post, I will explore the significance of reliability in database systems, which plays a crucial role in preserving data integrity and safeguarding against potential failures.
In the context of a database system, reliability implies that all data from a committed transaction must be securely stored in a nonvolatile location, protected from power outages, operating system glitches, and hardware malfunctions. PostgreSQL achieves this by writing data to the computer's permanent storage, typically using disk drives. The remarkable aspect is that even in the event of a catastrophic computer failure, as long as the disk drives remain intact, they can be moved to another computer with similar hardware, and all committed transactions will be preserved.
However, ensuring data is written to disk is not as simple as it sounds. Disk drives are much slower than main memory and CPUs, which leads to several layers of caching between the main memory and disk platters. To tackle this, PostgreSQL employs operating system buffer cache features to force writes from the cache to disk. Yet, there are additional caches in disk drive controllers and the disk drives themselves that can pose reliability hazards, especially those with volatile write-back caches.
To mitigate these risks, administrators must take measures like disabling write-back caching when necessary and choosing disk controllers with battery-backup units (BBUs) that preserve cache contents during power failures.
In any serious database system, reliability is of paramount importance, and PostgreSQL leaves no stone unturned in its pursuit of dependable operation. This makes it a powerful and robust solution for mission-critical applications where data reliability is crucial.
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