Why is SMR bad on FygoOS specifically?

FygoOS defaults to ZFS, and ZFS rebuilds after a drive failure read the whole surviving array while rewriting parity (RAIDZ1/2/3). SMR drives throttle whenever their cache fills up under sustained writes — exactly what a long rebuild does — so rebuilds can stretch from hours to days, extending the window in which a second drive fails. CMR drives absorb that workload.

How many drives does FygoOS let me use for free?

The free tier covers up to 4 storage devices (plus 3 users). More than that needs a Plus or Lifetime license. If you plan a 5- or 6-bay array, buy the drives to match the paid tier, not the free one — see our pricing guide. Figures per fygonas.com, Nov 2026.

FygoOS hard drives: why SMR is the trap in a ZFS build

Q: Which hard drives should I use with FygoOS?

NAS-class drives with 24/7 duty cycle and (for RAIDZ/dRAID pools) CMR, not SMR, recording: Seagate IronWolf/IronWolf Pro, WD Red Plus/Red Pro, Toshiba N300/MG series, Seagate Exos and WD Gold for heavier workloads. FygoOS has no whitelist, so the class of drive matters more than the brand.

FygoOS (the international edition of fnOS) is one of the few mainstream NAS OSes that makes ZFS its default and ships RAIDZ and dRAID as the array options. The official help docs cover install, volumes and 2FA — but they never say one thing the docs should: which drives survive what FygoOS does to them. That gap is what this page fills.

The rebuild is the killer, not the idle time

A ZFS pool rebuilt after a failure reads the entire surviving array while rewriting parity — hours of sustained, random-ish writes to every remaining drive. That workload punishes two drive classes:

SMR (shingled) drives — the cache fills, writes throttle, the rebuild that should take 6 hours can take 20+. Every extra hour is a second drive failing, uncorrectable.
desktop/office drives — their duty cycle (40–500 TB/yr) is far below what a 24/7 parity array does, and their firmware isn't tuned for long rebuilds.

dRAID's rotating parity makes it slightly more forgiving than classic RAIDZ — a rebuild touches fewer drives at once — but the SMR problem is unchanged: when a rebuild does hit an SMR drive, it still stalls.

The rule: CMR for every pool drive

Buy NAS-class, 24/7-duty-cycle, CMR drives for any RAIDZ/dRAID pool: IronWolf / IronWolf Pro, WD Red Plus / Red Pro, Toshiba N300 / MG series, Seagate Exos or WD Gold for heavy workloads. SSDs are fine as the system volume (FygoOS recommends it) and as a cache — they have no CMR/SMR distinction. The catch with "no whitelist": nothing stops you from putting a shingled 16 TB desktop drive in a 4-bay pool, and the pool will look fine until the first failure.

Check your part number — 765 CMR-rated, 30 SMR/mixed (of 3108 part numbers)

Our SMR/CMR checker covers the 795 rated part numbers we have on file across the official compatibility lists of five NAS vendors — the same ratings apply to FygoOS, because the recording technology is in the drive, not the OS:

Check a drive part number →

A "MIXED" rating means the manufacturer sells both SMR and CMR versions of the same series (e.g. WD Red — the small 2.5" and several large 3.5" capacities are shingled; the Pro line is CMR). Verify the exact part number, not just the series name.

Size the array around the free tier

The free FygoOS license caps you at 4 storage devices. A 4-bay RAIDZ1 pool of 4×16 TB CMR drives gives 48 TB usable and survives one failure — a sensible home build. Step up:

5+ bays or a 5th/6th device (cache + spare + pool) → you're over the free line: see FygoOS pricing before buying drives sized to the free tier.
Big single-drive capacities (16–24 TB) make every rebuild longer: URE probability climbs with capacity and platter count, which is why RAIDZ2 (two parity disks) is the safer default once you pass 6 drives — and our RAID capacity calculator shows the exact capacity and rebuild-time trade-off for your drive count in a minute.

What FygoOS does NOT tell you (yet)

FygoOS is young: no published per-drive compatibility list, no published drive-failure statistics, and no official statement (as of Nov 2026) on whether externally attached or cache drives count toward the free tier's 4-device limit. We flag those as "per official support" where we can't verify — re-check the official help portal before you commit.