OSS + ELC EU 2026

Every time you write data to or read data from a storage device in Linux, multiple caches are involved: the page cache (located in the memory) on the VFS layer, different kinds of caches on the storage devices (SSDs, HDDs) and controllers, and maybe filesystem-level or device mapper-level caches, too.

The caches help you to boost the I/O performance, but they also increase the risk of data loss in case of a sudden power outage. Understanding and configuring these caches correctly can be challenging, in particular if you are running virtualized systems and you have to set QEMU caching parameters (writeback, none, writethrough, directsync, unsafe), too.

In this talk, Werner explains how these caches work and shows you how to tune them for optimal performance while still being safe in case of a power outage.