Episode 509

Ask Noah Show 509

October 6th, 2026

53 mins 51 secs

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About this Episode

This week Steve gives us a deep dive into performance tuning, and we talk about how your body's memory functions.

-- During The Show --

00:50 Intro

  • Subsisting greeting variables
  • Accessible memory
  • Strength of memory
  • Reading and writing builds "Accessible memory"
  • Teaching builds "Strength of memory"
  • Go look up "space repetition"
  • Reader come home book
  • YouTube if you check their sources

17:55 News Wire

19:15 Performance Tuning

  • Defaults are someone guessing at a "safe option"
  • Three hosts being tuned
    • NAS (file server)
    • vHost (virtual disks live here)
    • Container Host
  • When should you performance tune?
    • Broadcasting
    • Networks (ISPs)
  • The more "dense" the more benefits
  • TuneD
  • ZFS "Adaptive Replacement Cache" (ARC)
    • Default is 50% of RAM
  • Swap file
    • System doesn't empty on its own
  • ARC stats
    • Hits and misses
    • Resets on reboot
  • Memory pressure
  • Swapyness
    • 60 is the default
    • the "cliff rate"
    • Tuned to around 10%-30% on "performance profiles"
    • System starts swapping before you hit zero RAM
  • ZFS record size
    • Record size is the "Maximum" not "Fixed size"
    • Media Library 1M
    • Postgres 16K
    • ZFS write amplification (8k writes to 1M records hurt)
  • AI study bot rules
  • Man systemd.directives
  • Write in and tell us if you want more!

Extra Credit: What to search after the show

  • ZFS ARC Tuning
  • ZFS Record Size
    • ZFS send receive preserves record size
    • Record size is per "data set" not directory
    • Record size only affects new writes
    • "zfs_dirty_data_max" vs "vm.dirty_ratio"
    • "QEMU "cache=none" O_DIRECT"
    • Postgres on NFS PGDATA caveats
  • "Tuned-adm virtual-host" hypervisor profile (The one nobody mentions)
  • Tuned profile format "sysctl" vs "main" the plugin/argument split
  • NFS mount options (the client side fix)
  • "vmstat" reading swap columns correctly

-- The Extra Credit Section --

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