· Atomic Racks
Building a 100TB+ Homelab Array on Used Enterprise Drives
The simplest 100 TB homelab array is eight 16 TB enterprise drives in RAIDZ2, which gives about 96 TB usable before file system overhead, or ten 14 TB drives for about 112 TB. Add an LSI 9300-8i HBA in IT mode, good airflow and a power supply sized for spin-up, and buy one drive model.
Pick a layout first
Capacity, redundancy and drive count are linked, so decide the layout before buying anything. The table uses decimal terabytes, the way drives are labeled. Operating systems report binary tebibytes, which are about 9 percent smaller, and ZFS reserves some space on top of that.
| Configuration | Raw | Usable (TB, before overhead) | Approx. TiB | Drives that can fail |
|---|---|---|---|---|
| 8x 16 TB, RAIDZ2 | 128 TB | 96 TB | 87 | 2 |
| 10x 14 TB, RAIDZ2 | 140 TB | 112 TB | 102 | 2 |
| 8x 18 TB, RAIDZ2 | 144 TB | 108 TB | 98 | 2 |
| 6x 18 TB, RAIDZ2 | 108 TB | 72 TB | 65 | 2 |
| 6x 18 TB, RAIDZ1 | 108 TB | 90 TB | 82 | 1 |
Six 18 TB drives look attractive but fall short of 100 TB usable with double parity. RAIDZ1 gets closer, but a single-parity array of 18 TB drives has a long rebuild window with no margin, so we do not recommend it at this size. If you are bay-limited to six, plan to add a second vdev later. If you have eight to ten bays, 16 or 18 TB drives in RAIDZ2 are the sweet spot.
Which drives
Three models cover most 100 TB builds well:
- Seagate Exos X16 16 TB SAS (ST16000NM002G): a common datacenter pull, often good value per terabyte if you already run an HBA.
- Seagate Exos X18 18 TB SATA (ST18000NM000J): SATA, so it also works on motherboard ports, with the highest capacity of the three.
- WD Ultrastar HC550 18 TB SAS (WUH721818AL4200): the WD alternative at 18 TB, check the sector format on the listing.
The Exos X16 vs X18 comparison and the HC530 vs HC550 vs HC570 comparison cover the differences. Whichever you choose, buy all array members as one model and capacity, so every drive has the same size, firmware behavior and performance.
Parts list
| Part | Example choice | Notes |
|---|---|---|
| Drives | 8x 16 TB or 8x 18 TB enterprise, one model | Plus one cold spare |
| HBA | LSI 9300-8i in IT mode | Two SFF-8643 ports, eight drives direct |
| Cables or backplane | SFF-8643 breakout cables, or a backplane | Expander backplane for more than eight drives |
| Chassis | 8 to 12 bay tower or rackmount with fans across the drives | Airflow over the drives and the HBA |
| Power supply | Quality unit sized for spin-up | Check 12V rail capacity |
| Memory | ECC RAM, 32 GB or more for ZFS | See RDIMM vs UDIMM |
| Boot | Small SSD mirror | Keep the OS off the data pool |
The HBA and backplane
An LSI 9300-8i (SAS3008 controller) in IT mode presents each drive directly to the operating system with no RAID layer, which is what ZFS, Unraid and SnapRAID all want. It runs both SAS and SATA drives at full speed. Two SFF-8643 ports with breakout cables connect eight drives directly. For more than eight, use a backplane with a SAS expander, which lets one HBA reach a full chassis of drives. The 9300 runs hot and expects server airflow, so point a fan at its heatsink in a tower case. Flash IT firmware before use if the card arrives in IR mode. Our SAS vs SATA guide covers mixed setups.
Power supply and staggered spin-up
A 3.5-inch drive draws its peak current from the 12V rail in the first seconds of spin-up, on the order of 2 A each. Ten drives starting together can ask for around 20 A on 12V, well above their running draw. Size the supply for that peak, or use staggered spin-up. SAS drives can wait for the HBA or expander to tell them to spin up, and many backplanes support staggered start. SATA drives support it through power-up in standby on some models. If neither is available, a supply with generous 12V headroom is the simple answer.
Cooling
Enterprise drives tolerate heat better than consumer drives, but running them cooler is still better for long life. Aim for drive temperatures in the 30s Celsius under load and avoid sustained readings in the high 40s. Densely packed drives in a tower with no front fans will run hot. Watch temperatures during the first scrub, which is the heaviest sustained load the array will see.
Power draw and electricity cost
A 3.5-inch helium enterprise drive draws roughly 5 W idle and 8 to 10 W active. Eight drives add roughly 40 to 80 W. A modest server board, HBA and fans add, for example, 50 to 100 W. A total average of 120 W is a reasonable example for planning.
The math: 120 W x 8,760 hours = 1,051 kWh per year. At an example rate of $0.15 per kWh that is about $158 per year; at $0.30 it is about $315. Use your own utility rate. Ten 14 TB drives draw a little more than eight 16 TB drives for similar capacity, which is one reason larger drives can be cheaper to own even when the purchase price per terabyte is similar. The calculator includes power cost.
ZFS, Unraid or SnapRAID
- ZFS (TrueNAS, Proxmox): checksums every block, self-heals from parity and gives the best data integrity. Drives in a vdev should match in capacity. Expanding a vdev one drive at a time is supported in recent OpenZFS versions, but planning the full width up front is still simpler. See best used enterprise drives for TrueNAS.
- Unraid: mixed capacities, add drives one at a time, spin down idle disks to save power. Parity must be at least as large as the largest data drive. See the Unraid parity drive guide.
- SnapRAID with mergerfs: snapshot parity computed on a schedule, suited to media libraries that change rarely. Data written since the last sync is unprotected.
For a 100 TB array that holds anything you care about, ZFS RAIDZ2 or Unraid with dual parity are the defaults. Either way, parity is not a backup.
Budgeting
Drives dominate the cost. As an example only, dated November 2026: if tested used 16 TB enterprise drives cost $10 to $15 per TB, eight of them plus one spare (144 TB raw) come to roughly $1,440 to $2,160. The HBA, cables, chassis and supply often add a few hundred dollars more, less if you reuse hardware. Prices vary week to week and by tier; lower-hour tiers cost more. For eight or more matched drives, a bulk quote gets you lot pricing and lets you ask for matched drives from one model and firmware.
FAQ
Is RAIDZ2 enough for 18 TB drives?
For eight to ten drives, yes. Above about twelve drives in one vdev, consider RAIDZ3 or two vdevs.
How long does a resilver take?
It depends on how full the pool is. Expect many hours to more than a day on a full 16 or 18 TB drive.
Can I mix SAS and SATA drives?
Yes, on a SAS HBA. Keeping one model per vdev is still the cleaner choice.
Do I need ECC memory?
It is strongly recommended for ZFS and for any server that runs continuously.
What we do at Atomic Racks
Every drive we sell passes a SMART extended self-test, a throughput benchmark and NIST SP 800-88 sanitization with read-back verification, as described on how we test. Hours are published per unit, each drive carries a QR tamper seal linking to its test report, and drives are priced into usage tiers with a tier-based warranty (see warranty). Browse 16 TB and 18 TB drives. Shipping is free within the US from Englewood, Colorado, with 30-day returns (buyer-paid return postage unless the item is defective).