When zram Makes Kubernetes Nodes Read From Disk

Fri, 07 Aug 2026 00:00:00 +0000

Kubernetes nodes whose image ships with a zram swap device can produce a continuous stream of major page faults under memory pressure. Nodes without zram do not show it.

The cause is two settings interacting on the same node, and the fix is a one-line change to one of them.

Diagnosis

The metric that exposes the behavior is node_vmstat_pgmajfault. A major page fault means that a page was not in memory and had to be fetched from a backing store. Under memory pressure, the rate can become continuously elevated rather than appearing as occasional spikes.

Sizing a JVM Container — Increasing the Limit is not Enough

Mon, 20 Jul 2026 00:00:00 +0000

Out of the box the modern JVM sizes its heap at 25 % of the container, for containers above roughly 500 MiB.¹ Almost nobody leaves it there, and nobody agrees on what to use instead. Red Hat’s OpenJDK images shipped 50 % for years, then moved to 80 %.² Plenty of guides say 75 %.³ Same problem, same JVM, four different recommendations and none of which account for the actual memory behavior of your application.

Articles on Ignacio Ballester

When zram Makes Kubernetes Nodes Read From Disk

Diagnosis

Sizing a JVM Container — Increasing the Limit is not Enough