Thus far in this book, we've discussed quite an array of functionality and methodology dedicated to keeping PostgreSQL systems online. By now, we have a burgeoning menagerie of replication utilities, system monitoring tools, connection pooling layers, and even a handful of troubleshooting tips. What could we possibly cover next?
As it turns out, simply installing PostgreSQL on a server can be done too early. Presuming that we have all of the hardware and software we discussed earlier, our servers are still missing the following three things:
The ability to synchronize data to two servers simultaneously
The capacity to freeze data to prevent changes for backup purposes
A durable filesystem designed for multiprocess I/O
There are several solutions for each of these missing elements, yet we've settled on three in particular: DRBD, LVM, and XFS. Let's explore a bit about each of these technologies and why we've chosen them to represent what we've deemed our Advanced Stack.