DiskPicker · the homelab value score

Every drive on DiskPicker gets a single homelab value score. It exists to answer one question the raw price-per-TB number can't: “is this a genuinely good drive to put in my NAS or home server right now, or is it just cheap?”

£/TB tells you what storage costs. It doesn't tell you whether the cheap drive is an SMR drive that will crawl during a RAID/ZFS rebuild, whether it's actually rated for always-on NAS duty, or how long it's warranted. The score folds those things into one number so a higher score always means “better bulk-storage value for a homelab”, not just “lowest price”.

A score around 100 is the reference point: a CMR drive at £18/TB — a genuinely great UK price, a little better than the cheapest drives usually on sale (~£23/TB right now). So today the best drives land in the 80s, mid-pack around 45, and a future bargain can push past 100. Higher is always better value; SMR and unknown-spec drives are pulled down regardless of price.

The formula

score = (18 / £perTB) × 100 // value vs an £18/TB reference × recordingFactor // CMR 1.00 · SMR 0.45 · unknown 0.85 × nasFactor // NAS-rated 1.10 · otherwise 1.00 × (1 + warrantyYears/100) // small nudge; defaults to 2yr if unknown

This is computed live in the database (the v_current_listings view), so the score on a drive always reflects its current price.

What each piece does — and why

1. Value vs an £18/TB reference — the base

(18 / £perTB) × 100. This anchors the whole score to real-world UK HDD pricing. £18/TB is set as a genuinely strong price — a bit below the ~£23/TB the cheapest large CMR drives typically sell for — so a great deal lands near 100 and there's headroom for an exceptional one to beat it. Halve the £/TB and the base doubles; double it and the base halves. It's deliberately linear so the score tracks price honestly.

Example: a drive at £18/TB → base = 18 / 18 × 100 = 100. At £24/TB → base = 18 / 24 × 100 = 75. At £36/TB → base = 50.

2. Recording technology — the big one

This is the factor a plain £/TB number can't capture on its own, and it's the one that actually bites in a homelab.

Recording techFactorWhy
CMR (conventional)×1.00 Full marks. Predictable write performance; safe for RAID/ZFS resilvers and NAS workloads.
SMR (shingled)×0.45 Heavily penalised. SMR can slow to a crawl under sustained random writes and can stall ZFS/RAID rebuilds — a real data-availability risk, not just a speed annoyance.
Unknown×0.85 A mild penalty for uncertainty: not punished like known SMR, but not trusted like confirmed CMR.
The 0.45 SMR multiplier is intentionally harsh. An SMR drive has to be more than twice as cheap per TB as a CMR drive to score the same — which reflects how much most homelabbers should avoid SMR for array use.

3. NAS-rated nudge

×1.10 if the drive is marketed/built for NAS duty (e.g. IronWolf, WD Red Plus/Pro, Exos, Ultrastar), otherwise ×1.00. NAS-class drives add vibration tolerance, higher workload ratings and firmware tuned for 24/7 array use. It's a 10% nudge, not a multiplier as strong as CMR/SMR, because a cheap reliable CMR desktop drive is still a fine homelab buy.

4. Warranty nudge

1 + warrantyYears/100. A small tie-breaker: a 5-year-warranty drive gets ×1.05, a 2-year gets ×1.02. Longer warranties correlate with higher-endurance drives and lower replacement risk, but it's deliberately minor so it never overrides price or recording tech. Unknown warranties default to 2 years so a missing spec doesn't unfairly tank the score.

Worked example

A Seagate IronWolf Pro 16TB (CMR, NAS-rated, 5-year warranty) at £24.75 per TB:

base = 18 / 24.75 × 100 = 72.7 × CMR (×1.00) = 72.7 × NAS-rated (×1.10) = 80.0 × warranty 5yr (×1.05) = 84.0

Now a hypothetical SMR archive drive at the same £24.75/TB (not NAS-rated, 2-year):

base = 18 / 24.75 × 100 = 72.7 × SMR (×0.45) = 32.7 × not NAS (×1.00) = 32.7 × warranty 2yr (×1.02) = 33.4

Identical price per TB, but the score ranks the CMR NAS drive ~2.5× higher — because for a homelab it genuinely is the better buy. (84 is currently about as high as the catalogue gets; nothing is cheap enough to reach 100 yet.)

How to read it

The score is a shortlisting aid, not gospel. It's tuned for the common case (bulk CMR storage in a NAS/ZFS box). If your use case is different — a cheap SMR drive purely for cold backups, or an SSD cache tier — read the badges and specs directly rather than chasing the highest number. The reference price and weights are deliberately simple and will be re-tuned as the UK market moves.