Three real options: (1) replace your drives with larger ones — usually the cheapest per terabyte thanks to resale recovery on the old drives, (2) add an expansion unit or a second NAS, or (3) archive cold data to LTO tape. Best value right now: replacing drives with larger ones, at about $27-29/added TB of usable capacity after you resell what you pull. Before you spend anything, delete and dedupe — it is free and often recovers 10-20%.
This is the default answer for most full NAS boxes, and in the 2026 market it is usually the cheapest per usable terabyte. You swap your existing drives, one at a time, for larger ones; when the last drive is in and the array has repaired, your usable capacity jumps. Crucially, you end up with a stack of perfectly good smaller drives you can resell — and because used drives are commanding prices at or near retail right now, that resale recovers a real fraction of the purchase.
Gross: four new 20TB drives at $310 each = $1,240. Resale: four old 8TB drives at $51-68 each = −$204-$272. Net: $968-$1,036 for +36TB usable — roughly $26.89-28.78 per added usable TB.
Pros: no new hardware to buy, power, or find space for; fewer, larger drives means fewer failure points and lower idle draw; and you raise your ceiling for the next few years. Cons: the swap spans about a week of one-at-a-time rebuilds, and in single-parity RAID the whole array runs degraded during each rebuild, so a verified backup is mandatory. Run your exact configuration through the upgrade planner, and follow the step-by-step replacement guide when you are ready.
The second path is to add capacity rather than replace it: attach an expansion unit to your existing NAS, or stand up a second NAS and populate it with new drives at today's live prices. At current pricing, four new 20TB drives alone run about $1,240 before the cost of the enclosure or expansion shelf — and unlike Option 1, there is no resale offset, because you are not retiring any drives. That makes the per-terabyte cost higher than an in-place upgrade in most cases.
Adding hardware wins in two specific situations. First, when your bays are already full at the largest capacity you can buy — you physically cannot upgrade in place, so more bays is the only way forward. Second, when you want a physically separate second system as a backup target, which is exactly what a proper 3-2-1 backup strategy calls for; in that case the "extra" hardware is doing double duty as resilience, not just capacity. Compare enclosures and bundle economics on the NAS devices page.
If a large share of what is filling your NAS is genuinely cold — finished projects, media you will not touch, compliance data — moving it to LTO tape frees the array without buying more spinning disk. At today's live pricing, LTO media runs about $5.44/TB (HPE LTO-9 Ultrium Single 18TB, 18TB per cartridge), the one storage medium the 2026 shortage has not price-spiked. The honest constraint is the hardware: an LTO drive and reader costs roughly two to four thousand dollars, so tape only pencils out above about 50TB of cold data, or if you can source a used LTO drive cheaply.
Tape is not a replacement for your live array — access is slow and sequential — but for archival it is unbeatable on cost per terabyte and, because tapes draw no power on the shelf, on long-term operating cost too. See the LTO tape tracker for full cartridge and library pricing.
Before spending a dollar, reclaim what you already have. Deduplicate repeated files, clear old snapshots and recycle bins (these quietly consume real space on most NAS filesystems), empty download and temp folders, and re-encode bloated media to modern codecs like H.265. This costs nothing but time and routinely recovers 10 to 20 percent of a "full" array — sometimes enough to defer an upgrade by a year. Do this first; then, if you still need capacity, choose from the three paid options above.
| Option | Upfront | Net after resale | $/added TB | Effort | Risk |
|---|---|---|---|---|---|
| Replace with largerBEST VALUE | $1,240 | $968-$1,036 | $27-29 | ~1 week of rebuilds | Degraded array during swaps |
| Add expansion / 2nd NAS | Drives + enclosure | No resale offset | Higher | 1-2 days setup | More power, more bays |
| Archive to LTO tape | $2-4k reader + $5/TB media | Reader amortized | $5/TB media | Setup + workflow | Cold access only |
| Delete / dedupe first | $0 | $0 | $0 | Hours | Recovers 10-20% |
You have three real options and one free one. First, delete and dedupe — clearing old snapshots, recycle bins, and re-encoding bloated media often recovers 10 to 20 percent at no cost. If you still need more, the three paid paths are: replace your existing drives with larger ones (usually cheapest per terabyte once you factor in reselling the old drives), add an expansion unit or a second NAS, or archive cold data to LTO tape. This page costs all three with live prices so you can compare net cost per added terabyte.
Replacing drives in your existing NAS is almost always cheaper per usable terabyte, because you reuse the enclosure, controller, and power supply and recover cash by selling the old drives. Buying a second NAS wins only when your bays are already full at the largest capacity you can buy, or when you specifically want a physically separate system as a backup target for a 3-2-1 strategy.
Not in standard RAID. In RAID 1, 5, 6, and 10 the array sizes itself to the smallest member, so a single larger drive gives you zero extra usable space until every drive has been replaced with the larger size. Synology SHR and UnRAID are the exceptions — they can deliver partial extra capacity after you swap the largest drives, without replacing the whole set.
Plan your upgrade when you cross roughly 80 to 90 percent of usable capacity. Most NAS filesystems slow down and fragment as they approach full, and you want headroom for the temporary space a RAID rebuild or data migration needs. Hitting 90 percent is the practical trigger to start pricing an upgrade rather than waiting until you are completely out of room.
In the current market, replacing your existing drives with larger ones is usually the cheapest way to add usable storage, because reselling the old drives offsets a meaningful share of the purchase. At today's live prices the best in-place upgrade path works out to about $27-29/added TB after resale recovery. Adding hardware or buying more small drives costs more per terabyte and consumes bays you will want later.
Rarely. LTO tape has the lowest raw cost per terabyte of any medium and is the one storage type not price-spiked by the shortage, but it requires a drive and reader costing roughly two to four thousand dollars. That only becomes rational above about 50 terabytes of genuinely cold data you will not touch, or if you can find a used LTO drive cheaply. For most home users, larger hard drives are the better answer.