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 new CMR drive at £18/TB — a price nobody in the UK is offering at the moment. The cheapest new CMR drive on the board today is £24.79/TB, so the top of the board sits near 70 and the median listing scores about 41. Higher is always better value; SMR, unknown-spec, used and recertified drives are pulled down regardless of price.

The reference is fixed, so the whole scale moves with the market. £18/TB was a stretch target when it was chosen; as UK drive prices have risen, every score has drifted down with them, and the top two bands below (Excellent 90+, Strong 74+) are currently out of reach — nothing on the board scores above 70. Read the score as a ranking and a comparison against the bands, not as a mark out of 100.

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 × warrantyFactor // 1 + (years − 2) × 0.05 · 5-yr ×1.15 · 2-yr ×1.00 × conditionFactor // new 1.00 · recertified 0.85 · used 0.75

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 was set as a genuinely strong price — below what the cheapest large CMR drives were selling for when the score was calibrated — so a great deal would land near 100 with headroom for an exceptional one to beat it. UK prices have since risen (the cheapest new CMR drive is £24.79/TB today), which is why nothing currently gets close: the anchor is a fixed constant, not a rolling market average, so the whole scale slides as the market does. 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 weight

1 + (warrantyYears − 2) × 0.05. Two years is the neutral baseline: a 1-year (grey-market/import) drive is nudged down to ×0.95, a 3-year gets ×1.05, and a 5-year NAS/enterprise warranty earns ×1.15. A longer manufacturer warranty is real value — cost per year of peace of mind, and it correlates with higher-endurance drives — but it's still weighted so it never overrides price or recording tech. Unknown warranties default to 2 years so a missing spec doesn't unfairly tank the score.

eBay is the exception: grey-market and recertified stock doesn't carry the manufacturer's warranty (that clock started when the drive first shipped, often years ago), so eBay listings are never credited with it. They get the seller's warranty where the listing states one ("3 Year Warranty"), otherwise assumed 1 year — the typical seller cover.

5. Condition

New ×1.00 · recertified ×0.85 · used ×0.75. A recertified or used drive can be a genuinely good buy — but it isn't the same product as a new one: shorter (or seller-only) warranty, unknown power-on hours, and no manufacturer support. The discount keeps a cheap second-hand drive from outranking a new drive purely on price, while still letting a truly outstanding recert deal surface near the top on merit. Condition is always shown next to the price, so you can see exactly why a drive scored the way it did.

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 (×1.15) = 92.0

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 (×1.00) = 32.7

Identical price per TB, but the score ranks the CMR NAS drive ~2.8× higher — because for a homelab it genuinely is the better buy. (Both examples are new drives, ×1.00; the same IronWolf Pro sold recertified would score 92.0 × 0.85 = 78.2.)

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.