PostgreSQL 10 High Performance - Third Edition

Write-back caches

The CPUs and memory in your server are quite fast compared to its disk drives. Accordingly, making the rest of the system wait for the disks, particularly when things need to be written out, can drag overall performance down heavily. Systems that wait for the disks to complete their writes before moving into their next task are referred to as having a write-through cache. While the data may be stored temporarily in a memory cache, until it's made it all the way through to the physical disk, any write an application requested isn't considered complete.

The normal solution to making that faster is to introduce a different type of write cache between the program doing the writing and disks. A write-back cache is one where data ...