MDD 18TB Hard Drive: Live Price, the Warranty Each Listing States, and Seagate Compared
We earn a commission if you buy through the links on this page, including links to the sellers it describes. You should read everything below knowing that. What we can offer against it is method: the figures here are computed from our own price database rather than supplied by anyone, the ownership facts come from public records we link, and we publish no rating or verdict on any seller - we show you what they sell, what the warranty covers, and how to check a drive yourself.
The cheapest MDD 18TB in stock is $489.99 - $27.22 per terabyte, used, SATA-6G, with a 5-year seller warranty stated. We track 3 MDD 18TB listings in stock among 15 18TB hard drives from 4 brands.
Every MDD listing was read at source on 1 October 2026. Prices and counts last refreshed
MDD is a label registered to GOHARDDRIVE, INC.; the drives are built by other manufacturers and sold under MDD's own part numbers. Who owns the label, and why no reliability data exists for it, are on the MDD reliability page. This page is about one capacity: what MDD has in stock at 18TB today, what each of those listings says about itself, and how it compares with the rest of the 18TB shelf.
MDD 18TB listings in stock
One row per product, cheapest per terabyte first. The warranty column is what each listing states; the line under the condition is the evidence for that offer. Prices are Amazon US listings, in US dollars.
Provenance describes the offer shown now, not the drive: Amazon's own condition and grade, the seller, the seller's note in their words, and what the listing title claims. It can change when a different seller holds the listing.
| MDD part number | Capacity | Interface | Condition and evidence | Warranty the listing states | $/TB | Price | |
|---|---|---|---|---|---|---|---|
| MDD18TSATA25672E | 18TB | SATA-6G | Used | 5 years (seller's) | $27.22 | $489.99 | Buy Now |
| MDD18TS25672NAS | 18TB | SATA-6G | Used | none stated | $28.33 | $509.99 | Buy Now |
| MDD18TSATA25672E | 18TB | SATA-6G | Used | 5 years (seller's) | $28.89 | $519.99 | Buy Now |
Each listing, in its own words
MDD18TSATA25672E is a SATA-6G 18TB drive, used, at $489.99 ($27.22/TB). The listing states a 5-year warranty, which is that seller's commitment.
MDD18TS25672NAS is a SATA-6G 18TB drive, used, at $509.99 ($28.33/TB). The listing states no warranty.
MDD18TSATA25672E is a SATA-6G 18TB drive, used, at $519.99 ($28.89/TB). The listing states a 5-year warranty, which is that seller's commitment.
Against Seagate at 18TB, matched
Where a Seagate 18TB listing is in stock at the same interface and condition as an MDD one, the two cheapest are compared per terabyte. A negative figure means MDD is cheaper. Model counts show how many distinct drives sit on each side of the match.
| Interface | Condition | MDD $/TB | Seagate $/TB | MDD vs Seagate | Models | Seagate |
|---|---|---|---|---|---|---|
| SATA-6G | Used | $27.22 | $32.22 | -15.5% | 2 / 1 | Buy Now Exos X20 18TB SATA |
At least one side of this match rests on a single model, so read it as one listing against another rather than as a market-wide figure. The all-capacity view, with every match and the mean and median across them, is on MDD vs Seagate.
The whole 18TB shelf, as levels
Every brand with a 18TB hard drive in stock, with its cheapest new and cheapest used price per terabyte. These are levels - the cheapest listing of each kind - not like-for-like differences: two brands' cheapest listings can be different interfaces and different drives.
| Brand | Listings in stock | Cheapest new $/TB | Cheapest used $/TB | Interfaces |
|---|---|---|---|---|
| WD | 10 | $42.54 | $28.33 | SATA-6G |
| MDD | 3 | none in stock | $27.22 | SATA-6G |
| Seagate | 1 | $39.72 | $32.22 | SATA-6G |
| Toshiba | 1 | $57.78 | $35.28 | SATA-6G |
Among the 4 brands with a used 18TB drive in stock, MDD's cheapest used listing ranks 1 of 4 by price per terabyte. The other brands on the 18TB shelf today are WD (10), Seagate (1), Toshiba (1). At this capacity MDD lists SATA-6G drives, and 2 of its 3 in-stock listings state a warranty. Those three facts - the interface, the condition and whose warranty applies - are the decision, more than the label on the drive.
Where the MDD 18TB listings differ from each other
The 3 MDD 18TB listings in stock are not interchangeable, and the differences are the reason to read each one. Today they run from $27.22 to $28.89 per terabyte for drives sold under the same label at the same capacity - two levels, not a like-for-like difference, because the cheapest and dearest can differ in interface and condition. 3 are used and 0 are sold as new under the label. 2 state a warranty and 1 do not. The cheapest is not automatically the one to buy: a listing that states a warranty, or that is sold as new rather than used, can be worth the difference, and the table above puts those facts beside the price so you can weigh them.
What 18TB drives give you in an array
Most people buying 18TB drives are filling a NAS or a server, so the useful number is usable space, not raw capacity. Synology documents how each RAID type turns drives into storage: RAID 1 gives the smallest drive's size, RAID 5 gives "(N – 1) x (Smallest drive size)" and RAID 6 "(N – 2) x (Smallest drive size)".
Company's own words Choose a RAID Type - DSM 7 Knowledge Center (capacity per RAID type), Synology. Read 1 October 2026.
Applied to 18TB drives: RAID 1 (2 drives) gives 18TB usable, RAID 5 (4 drives) gives 54TB usable and RAID 6 (4 drives) gives 36TB usable. At today's cheapest MDD 18TB listing ($489.99), RAID 1 costs $979.98 for the drives, $54.44 per usable terabyte, RAID 5 costs $1959.96 for the drives, $36.30 per usable terabyte and RAID 6 costs $1959.96 for the drives, $54.44 per usable terabyte. Those are drive costs only, at one listing's price; buying four drives usually means four different listings, so check each one's condition and stated warranty rather than assuming they match. For comparison, the cheapest used Seagate 18TB on the shelf is $32.22 per raw terabyte - a level, not a like-for-like match.The interface question at 18TB
Every MDD 18TB listing in stock is SATA, the interface of desktop NAS units and of every IronWolf we track, so interface is not the obstacle at this capacity. What the listings do not state is recording technology - none of them says CMR or SMR - and that is the question to put to the seller before one goes into an array. The mixing guide covers the rest of the checklist.
A cheap 18TB is a fair buy if you know what you are buying. Most MDD listings are used drives with a seller's warranty. Read the provenance line and the stated warranty for the listing you choose, check the drive's health the day it arrives, and keep it in a redundant array with a backup.
Before you buy an MDD 18TB
Settle the interface first: a SAS drive needs a SAS controller and cannot join a SATA pool, which the mixing guide covers in detail. Then read what the specific listing states about warranty, because at 18TB it differs from one MDD listing to the next - the warranty page explains whose promise it is. Recording technology is not stated by any MDD listing, so ask the seller if your array needs CMR. And on arrival, read the drive's health data inside the return window and compare it with what the listing said.
Frequently asked questions
Frequently asked questions
How much is an MDD 18TB hard drive?
The cheapest MDD 18TB listing in stock is $489.99 ($27.22 per terabyte), used, SATA-6G. We track 3 MDD 18TB listings in stock; prices are Amazon US.
What warranty does the MDD 18TB have?
It depends on the listing: of the 3 MDD 18TB listings in stock, 2 state a warranty (5 years) and 1 state none. A stated warranty is the seller's, not a drive maker's.
Is the MDD 18TB cheaper than a Seagate 18TB?
Matched at the same interface and condition: SATA-6G used, MDD -15.5% against Seagate (2 MDD / 1 Seagate model).
How much usable space do four MDD 18TB drives give?
Using Synology's documented formulas: RAID 5 gives (N - 1) x the smallest drive, so four 18TB drives give 54TB usable; RAID 6 gives (N - 2) x the smallest, 36TB. At today's cheapest MDD 18TB price, four drives cost $1959.96, or $36.30 per usable terabyte in RAID 5.
Is the MDD 18TB SATA or SAS?
In stock right now: 3 SATA and 0 SAS. A SAS drive needs a SAS controller and, per Synology's documentation, cannot share a storage pool with SATA drives - so check the interface of the specific listing before you buy.
Is the MDD 18TB CMR or SMR?
No MDD listing states a recording technology, and our CMR/SMR resolver has no MDD part number on record, so we show it as unknown and never assume CMR. Ask the seller before using one in a NAS.
Is the MDD 18TB new or used?
3 of the 3 in stock are used. A listing Amazon reports as new is, on this site, "sold as new under the MDD label": MDD is a label, so it cannot carry a manufacturer's warranty.
Related: MDD: who makes them · Is MDD reliable? · MDD warranty · Mixing MDD with IronWolf · MDD vs Seagate · Refurbished vs recertified vs renewed