TL;DR: The pool had the default cachefile=-, but Talos has no normal writable /etc/zfs location for zpool.cache. OpenZFS kept failing to write the cachefile and retrying SPA_ASYNC_CONFIG_UPDATE every 300 seconds. Setting zpool set cachefile=none hdds stopped the config_sync loop, and the drives stayed in standby past the old wake interval.
This was found with Codex/GPT-5.5 after about 2 hours of debugging, using a mix of tracing, disk-sector inspection, Talos debugging, and eventually reading the relevant OpenZFS source.
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I migrated a Kubernetes node from NixOS to Talos Linux. Same OpenZFS version: 2.4.1.
After the migration, HDDs in a ZFS pool would no lon



