fsync promises two things, durability and ordering, and I only need ordering. ext4 gives both or neither: every fsync commits the journal and flushes the disk cache. ZFS with sync=disabled gives ordering alone: transaction groups land in order, and a crash loses the last tens of seconds, not a database. My two HDDs are 2.7% busy instead of 13%, and a write takes 2 ms instead of 16.
My TP-Link EAP770 v1 corrupts downloads over Wi-Fi and TP-Link EOL'd it before I unboxed it. The fix is two zeros in sysfs. TP-Link's shell won't let me write them, so I wrote a kernel exploit for my own fucking access point.
When you cancel an async task that has spawned a blocking thread, the async mutex guard gets dropped but the thread keeps running unprotected. Always pass owned guards to spawned threads.