NAS drive buying guide 2025: when 18TB used enterprise is the right call

The HDD market in September 2025 looks different from twelve months ago. The r/DataHoarder thread on 96.4% price increases (4407 upvotes) is the canonical document of how the AI training boom has eaten into HDD supply chains, driving prices up sharply. For NAS / homelab buyers, the calculus has shifted.

This guide is from building multiple homelab pools across 2024–2025, plus tracking the community pricing reports.

The current state of HDD pricing

In mid-2025 the working math:

• 22-26TB drives: brand-new enterprise SKUs are $400-600 (varies by week). Up significantly from 2024.
• 18TB drives: the sweet spot. New retail $300-400; used enterprise $150-250.
• 14-16TB drives: cost per TB approaches 18TB+ tier; rarely the right pick.
• Anything under 12TB: new builds skip these. Old gear gets used drives at $50-100.

The community signal: used enterprise drives are now competing with new consumer drives on quality AND price in a way they weren’t two years ago. The 3209-upvote “56TB for $300” thread captures the deal-hunting era we’re in.

The working buying strategy

For a 2025 homelab build:

1. Used 18TB enterprise drives from reputable resellers

The sweet spot. Sources:

• ServerPartDeals — long-standing reseller, decent warranties on used enterprise
• GoHardDrive — competitive pricing, mixed warranty experience
• WeBuyUsedTape (WBTU) — surprisingly good for bulk enterprise drives
• Local data-centre auctions if you can attend in person

Expect 3-5 years of power-on hours on used enterprise drives. With ZFS, this is genuinely fine if you SMART-test before deploying.

2. Burn-in before deploying

Non-negotiable for used drives. The process:

# Test for bad blocks (destructive — empty drive only)
badblocks -wsv /dev/sdX

# Or smaller test for confidence (one badblocks pattern)
badblocks -wsv -t 0x55 /dev/sdX

Burn-in takes 24-48 hours for an 18TB drive. Catches infant mortality (drives that fail in the first few hundred power-on hours). The 1% of drives that fail burn-in were the 1% that would have failed in your pool a month after deployment.

3. Mix vendors, not just models

Buy 2 WD + 2 Seagate of similar capacity rather than 4 of the same drive. The 5-10% premium is the cheapest insurance against batch-level firmware bugs or MTBF correlation.

4. Track SMART before commitment

Run smartctl -a /dev/sdX on every new drive. Check:

• Reallocated_Sector_Ct: anything > 0 is a return
• Current_Pending_Sector: anything > 0 is a return
• Offline_Uncorrectable: anything > 0 is a return
• Power_On_Hours: high is OK on enterprise (5-year warranty enterprise drives run 24/7); high on consumer SMR drives is a worry

Used enterprise with 30,000 power-on hours that passes SMART is more reliable than new consumer with 0 hours that hasn’t been stress-tested.

What to specifically avoid

Don’t buy:

• Consumer SMR drives — write performance collapses under sustained load. WD Red SMR is the classic trap; check for “CMR” in the spec sheet
• Drives without published warranty terms — eBay grey market is a roll of the dice
• Shucked external drives for ZFS pools — power-pin behaviour and warranty caveats make these riskier than direct internal enterprise
• Refurbished consumer drives — refurb on consumer drives is usually a worse deal than used enterprise

The AI-boom-effect on prices

The 1742-upvote “Hard drives already sold out” thread captures the supply squeeze. AI training infrastructure consumes massive HDD capacity for cold storage of training datasets; the hyperscalers are eating supply that previously trickled down to consumer / NAS buyers.

Practical implications:

• Don’t wait for prices to drop — they’re unlikely to in the near term. Buy when you see fair pricing.
• Build smaller, expand later if budget is tight — a 4-drive 18TB pool with future-RAIDZ-expansion is more economical than a 6-drive build all at once.
• Used enterprise market is now the smart-money market — buyers who avoided it in 2023 should reconsider in 2025.

A real shopping list for September 2025

For a quiet 4-bay homelab build (~$1,300 budget):

• 4× used 18TB Toshiba MG09 or WD HC560 from ServerPartDeals at ~$170-200 each = ~$700
• Burn-in 48 hours each (sequential, OK to overlap if your dock supports multi-drive testing)
• Deploy as 2× mirror vdevs in ZFS (covered in our ZFS pool design guide)
• ~36TB usable, $700 in drives, plus your mini PC ($400-500) and DAS chassis ($300)
• Total system: ~$1,400-1,500 for a quiet, fully-redundant 36TB NAS

This is the build that competes with the $1,500 Synology DS923+ + drives in functionality but with full open-source software and your choice of platform (TrueNAS, Proxmox, etc.).

The bigger pattern

The HDD market in 2025 isn’t the cheap-supply commodity it was through the late 2010s. Buying smart now means:

• Used enterprise from reputable resellers
• Burn-in discipline before deployment
• Mixed vendors and models
• ZFS / mirror topology that tolerates the higher failure rate of used drives

Done right, you build a 30TB+ NAS for ~$1,000 in drives in 2025. Done wrong, you spend the same and end up with a flaky pool. The discipline matters more in 2025 than it did in 2022.

For the storage topology, see our ZFS pool design guide. For the wider build context, Building a quiet homelab server and Proxmox VE review.