The Great Home Server Showdown: FIO vs PAO
My media server was driving me absolutely insane. Seriously. Every night, the kids would fire up their stupid cartoons, the wife would start binging some obscure European crime show, and I’d be in my office trying to pull down 100GB of work files. And what happened? Everything stuttered. The whole damn house network just seized up like an old engine running on sludge. I knew it was the disks, but I couldn’t prove which setup was the real culprit. This whole thing started because I needed to stop guessing and start measuring.
I had been running two radically different storage approaches on the same box, just experimenting. One was an older, simpler configuration I called FIO (Fast Is Optimal)—just a couple of decent SSDs in a basic linear raid array, standard sequential queueing. Reliable, but not exactly designed for heavy concurrent hits. The other was my complicated new baby, which I dubbed PAO (Parallel Access Optimized). This thing was built around trying to squeeze every drop of concurrent performance out of newer NVMe drives by setting up massive asynchronous queues and forcing parallel access across multiple threads.
The theory sounded great. PAO should demolish FIO in a real-world multi-user environment. But theory and reality, especially when dealing with cheap components bought during a midnight sale, often diverge violently. I decided I was going to push them both until something broke, or until I had numbers I could trust.
Setting Up the Gauntlet
I dedicated a solid week to just setting up the testing environment. It wasn’t a clean bench setup, mind you. This was done on a folding table next to the furnace in the basement. I pulled out the old spare drives—an older SATA SSD for the FIO testbed and a brand new, slightly overheating NVMe stick for PAO. I had to rip out a bunch of insulation just to make space for the cooling fans I slapped on the NVMe because that thing ran hotter than the sun.
The practice itself was grinding. I didn’t bother with synthetic benchmarks. I ran real-world simulations. I wrote a script that simultaneously:
- Fired off four concurrent 4K random read streams (simulating the kids streaming).
- Executed two massive sequential write streams (my work files downloading).
- Ran a third, small block sequential read/write test (the system logging and metadata updates).
I hammered FIO for eight hours straight, then immediately swapped the load over and hammered PAO for another eight hours. I logged IOPS, average latency, and, crucially, the 99th percentile latency—that’s the metric that tells you how bad those awful stutters really are.
The Unexpected Interruption
I was in the middle of the second day of testing PAO when everything went sideways. I was watching the latency spikes, ready to call it a night, when my phone rang. It was my boss. Turns out, the massive project I was supposed to be delivering next week? They decided to pull the plug on the entire division. Just like that. Done. Out of a job. After six years of busting my butt for them, they just dropped the axe with a five-minute call.
I was furious, obviously. And suddenly, I had a lot of free time. Like, all the time in the world. Instead of panicking and updating my resume immediately, I did something stupid. I went back to the basement. I figured, since the universe had just dumped a load of garbage on my head, I might as well get some damn closure on my storage problem. I cranked the tests up even higher. I wasn’t just testing my server anymore; I was testing my sanity.
Who Won, and Why It Didn’t Matter
The data I gathered was messy, but the conclusion was sharp.
PAO, the complicated NVMe setup, absolutely destroyed FIO in terms of pure average IOPS and throughput under heavy load. It was faster by about 40%. The raw speed was there. If I was running a massive database, PAO would win, hands down.
But then I looked at the latency, specifically the 99th percentile. This is where the stuttering happens, the annoying lag that makes everyone yell at the server.
- The FIO setup, despite being slower overall, had incredibly stable latency. It performed consistently poorly, but predictably so.
- The PAO setup, because it was juggling so many concurrent threads, had occasional, massive latency spikes—sometimes jumping from 2ms to 300ms.
That 300ms spike? That’s the exact moment the cartoon freezes and the wife glares at the router. FIO was slow but reliable. PAO was fast but prone to catastrophic hiccups.
The irony is that after losing my job and having nothing but time to stare at these metrics, I realized I was optimizing for the wrong thing. I didn’t need the fastest theoretical server; I needed the server that wouldn’t make my family angry. I ended up decommissioning the shiny PAO setup and migrating all the streaming and file-serving duties back to the older, slower, but infinitely more stable FIO configuration.
So, who wins? PAO wins the speed contest. But FIO wins the ‘keeping your family from unplugging your server and throwing it into a river’ contest. Given my new situation, stability over speed feels like a crucial life lesson, not just a technical one.