Fewer Big Drives or More Small Ones? What Every Capacity Actually Costs Per TB (August 2026)
There is a thread on r/unRAID with a title that is the whole question in six characters: 2 x 24TB or 1 x 28TB?
The replies do what replies always do. Someone argues for spindles, someone argues for slots, someone says buy bigger than you think. All of it is reasonable and none of it comes with a number attached. The one person who did reach for a number could not tell whether it was a good one:
“Though it wasn’t really a ‘sale’ at $21 per TB. Now, the 28TBs are back in stock at that same $21/TB price. Technically they are on sale, but in reality, it’s just the original price.”
- u/SeaVolume3325, who started the thread
And underneath every one of these threads, the same regret, from people who already made the choice:
“Lol I learned within a year that if you think the drive size you picked is large enough for what you plan on using it for…you’re wrong. […] Here I am a year later going ‘fuck, I should have went with 18-20TB drives instead.’”
- u/CrzyJek, r/unRAID
“I have 12tb + 16th drives but I kind of regret I didn’t go 24tb ones right away. One 24tb would be almost the same storage as 2 drives I have right now.”
- u/positivcheg, same thread
I track every drive listing on Amazon.com and recompute price per terabyte daily, so I can put the missing number on this. Below is what every capacity costs right now, and then the part that surprised me, which is that the obvious reading of the table is wrong.
Everything here is live data pulled on 5 August 2026: 1,434 internal 3.5” SATA hard drives at 2 TB and above on Amazon.com, all conditions, 1,099 of them repriced today.
The whole price curve
Three columns, because one number will mislead you. Floor is the single cheapest live listing. 25th percentile is cheaper than three quarters of the shelf, which is roughly what an attentive buyer actually pays. Median is the middle listing, which is roughly what you pay if you search the capacity and buy something sensible-looking.
| Capacity | Listings | Floor $/TB | 25th pct $/TB | Median $/TB |
|---|---|---|---|---|
| 2 TB | 171 | $17.00 | $49.00 | $68.54 |
| 3 TB | 98 | $8.33 | $34.75 | $45.00 |
| 4 TB | 200 | $18.25 | $41.25 | $54.87 |
| 6 TB | 184 | $24.67 | $36.67 | $54.16 |
| 8 TB | 175 | $26.12 | $43.53 | $62.48 |
| 10 TB | 167 | $22.08 | $38.00 | $52.00 |
| 12 TB | 124 | $24.92 | $33.25 | $43.75 |
| 14 TB | 90 | $23.50 | $30.71 | $47.90 |
| 16 TB | 93 | $25.56 | $39.31 | $47.44 |
| 18 TB | 39 | $25.55 | $29.17 | $35.83 |
| 20 TB | 28 | $29.00 | $31.37 | $40.92 |
| 22 TB | 13 | $29.95 | $30.00 | $37.73 |
| 24 TB | 19 | $27.50 | $28.52 | $31.21 |
| 26 TB | 12 | $26.12 | $26.92 | $42.08 |
| 28 TB | 6 | $26.39 | $26.75 | $26.75 |
Read the last two columns against each other and you get a genuine puzzle.
The median falls off a cliff. $62.48/TB at 8 TB down to $26.75/TB at 28 TB. The typical 8 TB drive costs 134% more per terabyte than the typical 28 TB drive. That is the strongest version of “buy bigger” anyone has put a number to, and it says the regret in those threads is correct.
The floor barely moves at all. From 8 TB to 28 TB the cheapest listing sits between $22.08 and $29.95/TB with no trend worth the name. If you are the sort of person who reads every listing on the page, capacity looks like it stops mattering.
Those two facts pull in opposite directions, and the obvious conclusion from the second one is that a careful buyer can ignore capacity entirely and buy whatever size fits the case. I believed that for about twenty minutes. Then I checked how many listings are actually down there.
The floor is one listing deep at 4 TB and the entire shelf at 28 TB
Here is the count of listings priced within 10% of the cheapest one, at each capacity:
| Capacity | Listings within 10% of the floor | Out of |
|---|---|---|
| 4 TB | 1 | 200 |
| 8 TB | 3 | 175 |
| 12 TB | 4 | 124 |
| 16 TB | 3 | 93 |
| 20 TB | 9 | 28 |
| 24 TB | 9 | 19 |
| 28 TB | 6 | 6 |
At 4 TB, the floor is a single listing out of two hundred. At 28 TB, every listing on the shelf is within 10% of the cheapest one.
That changes the answer completely, because you are not buying one drive. You are filling a machine.
“Shop the floor and capacity stops mattering” is true for one drive and false for a build. To reach 48 TB in 4 TB drives at the floor price, you would have to find that one unicorn listing out of two hundred and then buy twelve of it. That is not a purchase, it is a scavenger hunt with twelve stages, and the stock is not there. To reach 48 TB in 24 TB drives at the floor price, nearly half the shelf already qualifies and you need two.
Big drives are not just cheaper on average. They have a floor you can actually reach, repeatedly, without hunting. That is the real answer to the fewer-versus-more question and I have not seen anyone say it.
The same build, three ways
48 TB usable-ish, before parity. Three price routes: buying at the floor, buying attentively at the 25th percentile, and buying the median listing.
| Drive size | Drives needed | At the floor | At the 25th pct | At the median | Bays used | Idle watts |
|---|---|---|---|---|---|---|
| 4 TB | 12 | $876 | $1,980 | $2,634 | 12 | 60 W |
| 6 TB | 8 | $1,184 | $1,760 | $2,600 | 8 | 40 W |
| 8 TB | 6 | $1,254 | $2,089 | $2,999 | 6 | 30 W |
| 10 TB | 5 | $1,104 | $1,900 | $2,600 | 5 | 25 W |
| 12 TB | 4 | $1,196 | $1,596 | $2,100 | 4 | 20 W |
| 14 TB | 4 | $1,316 | $1,720 | $2,682 | 4 | 20 W |
| 16 TB | 3 | $1,227 | $1,887 | $2,277 | 3 | 15 W |
| 18 TB | 3 | $1,380 | $1,575 | $1,935 | 3 | 15 W |
| 20 TB | 3 | $1,740 | $1,882 | $2,455 | 3 | 15 W |
| 24 TB | 2 | $1,320 | $1,369 | $1,498 | 2 | 10 W |
The floor column is the fantasy version, and I include it precisely because it is the one people argue from. It says twelve 4 TB drives for $876 is the cheapest way to 48 TB, which is arithmetically true and practically impossible, for the reason in the previous section.
The 25th percentile column is the honest one, and it says something clean: 12 TB, 18 TB and 24 TB all land between $1,369 and $1,596, while 4 TB and 8 TB cost $2,000 or more for the same capacity. The small-drive penalty is real and it is roughly $400 to $700 on a 48 TB build.
And look at the 24 TB row across all three columns: $1,320, $1,369, $1,498. The spread from the very best listing to the middle of the shelf is 13%. On the 4 TB row it is 200%. At the top of the capacity range, you almost cannot get this wrong. At the bottom, getting it right requires work that will not scale to twelve units.
One more thing about that floor column, and it connects to what I wrote yesterday about used drives: 175 of the 192 listings in the cheapest quartile at 8 TB and above are used or recertified. The floor is the used market, essentially without exception. At 28 TB there is not a single new listing on Amazon.com in my data today, only used. So “shop the floor” and “buy used” are the same strategy wearing different clothes, and everything in that piece about warranties applies here too.
The two questions people actually asked, priced
“2 x 24TB or 1 x 28TB?”
| Option | Capacity | Today’s cheapest | $/TB |
|---|---|---|---|
| 2 x 24 TB | 48 TB | 2 x $659.99 = $1,319.98 | $27.50 |
| 1 x 28 TB | 28 TB | $739.00 | $26.39 |
$1.11/TB apart. Price is not deciding this one, which means the thread’s most sensible reply was right without needing the data:
“At the same price per TB the 28TB gives you more flexibility for future parity upgrades but two 24TBs gives you redundancy options sooner.”
- u/Realistic-Reaction40, same thread
So decide it on bays and parity, not dollars. If you have slots to spare and want redundancy now, take the two. If slots are tight and you expect to keep growing, take the one and keep the bay.
“4 x 6tb ironwolf vs. 2 x 12tb WD red plus”, from r/homelab:
| Option | Capacity | Today’s cheapest | $/TB | Bays | Idle |
|---|---|---|---|---|---|
| 4 x 6 TB | 24 TB | 4 x $148.00 = $592 | $24.67 | 4 | 20 W |
| 2 x 12 TB | 24 TB | 2 x $299.00 = $598 | $24.92 | 2 | 10 W |
Six dollars apart. The thread landed on the right answer anyway:
“Cost being equal i would get the 2 12gb dives so you have room to expand storage down the line.”
- u/FluffyWarHampster
“Having larger drive saves on power, is more flexible and less work overall. Go with 2x12”
- u/blue_eyes_pro_dragon
Cost was equal, and they were right that it therefore comes down to the two free bays. What the thread could not know is that the tie was real. Note though that both of these are floor prices at 6 TB and 12 TB, which is exactly the four-listings-out-of-124 problem. At the 25th percentile the same comparison is $880 for four 6 TB against $798 for two 12 TB, and the big drives win outright.
So what should decide it
If price per TB is roughly a wash at the floor and clearly favours big drives at the median, the tiebreakers matter. Here they are with numbers on them, because that is what these threads never have.
Bays, which is the constraint that actually bites
Every drive you buy small is a bay you cannot use later. That is the thing behind every “room to expand” reply in every thread. A 4-bay NAS filled with 6 TB drives is a 24 TB machine that is finished, and your only upgrade path is throwing drives away. The same box with 18 TB drives is a 72 TB machine with the same power draw and the same noise.
This is the single strongest argument for going big, and it is not a price argument at all.
Power, priced honestly
People guess at this and stop. The arithmetic, assuming about 5 W idle per 3.5” drive running 24/7 at $0.15/kWh:
| Drives | kWh/year | Cost/year |
|---|---|---|
| 2 | 88 | $13 |
| 3 | 131 | $20 |
| 4 | 175 | $26 |
| 6 | 263 | $39 |
| 8 | 350 | $53 |
| 12 | 526 | $79 |
Twelve 4 TB drives cost about $66 a year more to run than two 24 TB drives. Over five years that is $330, which is not nothing, but it is smaller than the $400 to $700 purchase-price gap and much smaller than people in these threads seem to assume. Substitute your own rate and idle figure; the ratio is what matters, and idle draw varies by model.
Except in Europe, where the sums are different enough to change the answer outright:
“I managed to snag 60 of them for 30 euros… why… because 120 tb for 30 euros. Now as to what to do with them… im absolutely not making a 60 drives nas. The scam electricity prices in Europe make it impossible.”
- u/AuraLiaxia, r/DataHoarder
Free drives that you cannot afford to spin are not free. Worth doing your own arithmetic before accepting a pile of small drives from anyone.
Rebuild time, which is the real cost of a big drive
This is where the spindle argument earns its keep, and it is the one genuine downside of going big.
At an assumed 200 MB/s sustained (optimistic for a full-surface parity rebuild on a busy array, but it makes the ratios clear):
| Drive | Rebuild window |
|---|---|
| 4 TB | ~6 hours |
| 8 TB | ~11 hours |
| 12 TB | ~17 hours |
| 16 TB | ~22 hours |
| 20 TB | ~28 hours |
| 24 TB | ~33 hours |
| 28 TB | ~39 hours |
I have not benchmarked this and your array will be slower, probably much slower if it is doing anything else at the time. Treat the shape rather than the absolute values: a 28 TB rebuild is a day and a half of degraded array, against six hours for a 4 TB one. That is a day and a half during which a second failure is not survivable on single parity.
Someone in r/homelab worked through the related unrecoverable-error argument in public, badly served by anything they could find:
“Most NAS drive have once in 10 14 failure rate, which is single bit error per 12.5TB. If I have four 6 TB drive with raid 5, the available storage is 18TB… Anyhow, with stripped mirror it would be safer, because that single bit error is not statistically signifcant anymore, since you are rebuilding only 6TB at a time”
- u/siegevjorn, r/homelab
They are reasoning correctly. The practical answer most people land on is not “buy small drives”, it is dual parity above about 16 TB, which costs you one more drive and removes the whole problem. That is a better use of a bay than a second small drive.
If you run Unraid, one worry you can drop
A lot of this demand comes from Unraid users, and there is a persistent worry about matching capacities that simply does not apply:
“There is no practical benefit to having the same drive sizes in Unraid. That’s sort of the point. Get the drives that provide you the most storage for the least $/gb!”
- u/Medical_Shame4079, r/unRAID
That is right, with one constraint worth planning around: parity has to be at least as large as your largest data drive. So the first time you buy a drive bigger than your parity, you are buying two drives, not one. That is the hidden cost of stepping up capacity later, and it is a reason to buy the bigger parity drive at the start rather than the second time.
What this doesn’t cover
These are Amazon.com prices, in dollars, for the US market. That is the only market I track, deliberately. Half the people asking this question are not in it, and the European answers in particular come out differently because of electricity, VAT and a much thinner used market.
I also cannot see stock depth. When I say a listing sits at $18.25/TB, I mean one listing is at that price today. I cannot tell you whether the seller has one of them or forty, and the whole floor-depth argument above is exactly why that matters. Assume the unicorn listings are one-offs unless you check.
My own answer, for what it is worth
I run Unraid, and I ended up there for a reason that shows up nowhere in the price tables: I wanted to add a drive whenever I could afford one, rather than buy a matched set. Being too tight to buy new drives is the whole design constraint. Failures are planned for rather than feared.
So my array is a hodgepodge of WD Reds and some cheap SMR drives that probably should not be in there, bought whenever something looked good. On hot days the temperature warnings pile up around 118F (48C) and it copes.
Having done this arithmetic, the thing I would tell my past self is not “buy bigger”, which everyone already says. It is narrower: buy the biggest parity drive you can afford first, because that is the purchase that decides what every later purchase is allowed to be. The rest of the array can be whatever was cheap that month, which is how mine got built anyway.
Bottom line
As of 5 August 2026, on Amazon.com, internal 3.5” SATA drives:
- The median 8 TB drive costs 134% more per TB than the median 28 TB drive ($62.48 against $26.75). The regret in those threads is well founded.
- The floor is nearly flat from 8 TB to 28 TB, roughly $22 to $30/TB, which looks like it lets careful buyers ignore capacity.
- It doesn’t, because the floor is one listing deep at 4 TB and six out of six at 28 TB. You can buy the cheap 28 TB drive twice. You cannot buy the cheap 4 TB drive twelve times.
- On a realistic 48 TB build, small drives cost $400 to $700 more and use three to six times the bays.
- The floor is the used market: 175 of the 192 cheapest listings at 8 TB and above are used or recertified.
- 2 x 24 TB versus 1 x 28 TB is $1.11/TB apart. Decide it on bays and parity, not price.
- The one real cost of going big is rebuild time, roughly 39 hours at 28 TB against 6 at 4 TB. The answer to that is dual parity, not smaller drives.
For live prices by capacity, cheapest HDD per TB ranks everything I track, and the per-capacity pages cover 16 TB, 12 TB, 8 TB and 4 TB specifically. To check a listing you already have open, the good price per TB benchmark has percentile bands by tier. Since the floor is the used market, refurbished and used drives covers what to check before you pay. And if you are still sizing the build itself, the storage calculator will do it.
Prices in this article were pulled from live Amazon.com listings on 5 August 2026 and cover 1,434 internal 3.5” SATA hard drives at 2 TB and above. Power and rebuild-time figures are stated assumptions, not measurements, and are labelled as such. Reddit quotes are from public threads, linked at each quote. HDDHunt earns a commission on purchases made through links on this site, at no extra cost to you. See the affiliate disclosure.