What two 4TB drives provide in RAID1
Two WD4005FFBX drives in RAID1 still give about 4 TB of usable space after filesystem overhead, not 8 TB. RAID1 is not a backup.[1]
Western Digital · NAS hard drive buying guide
WD Red Pro 4TB (WD4005FFBX) Buying Guide
Product facts and dated cost
Western Digital WD Red Pro 4TB · Exact identity: WD4005FFBX
4TB decimal capacity · CMR · SATA 6 Gb/s
Catalog amount: $244.99 · historical · Price record: 2026-10-05T02:09:41.687501+00:00. Tax and shipping excluded.
Historical price observation. Recheck the price and availability before buying; this is not a current offer.
WD Red Pro 4TB: specifications and dated store comparison →A 4TB air CMR Red Pro: 267 MB/s on the data sheet and 217 MB/s on the store page — an unresolved official conflict — and still no lab test of this MPN.
One retail 4TB 3.5-inch SATA WD4005FFBX. Enclosure, extra drives and RAID are separate.
This page uses Western Digital’s January 2025 WD4005FFBX column (including footnotes 5–8), the 2026-09-11 US store SKU page, dated US listings, and one Kakaku stopgap hot-swap note by サイクロンエフェクト. ChooseCompute has not tested the drive. Older Red Pro 4TB reviews are different MPNs. See the review evidence ↓
Is this 4TB drive right for your NAS?
Key hard drive specifications
Full specifications ↗Follow any specification for its full conditions and sources.
Living with it
Capacity, NAS workload and the 217 vs 267 MB/s conflict
Power is the low column in this air trio
Average read/write 5.8 W and idle 4.0 W are the 4TB cells. 6TB and 8TB air columns are 6.9/4.9 W. That is a rating, not a measured NAS pack.[1]
What an exact WD4005FFBX test still has not shown
Our buying advice combines official specifications with the original reviews below. We have not tested this product ourselves. Expand a review for its setup, measurements and limitations.
Kakaku.com user review
サイクロンエフェクトNov 24, 2024
サイクロンエフェクト: short-term HP NAS RAID6 hot-swap
On 2024-11-24 the Kakaku user サイクロンエフェクト hot-swapped WD4005FFBX into an unnamed company HP NAS RAID6 without formatting, as a months-long stopgap until a new NAS. Not a speed, noise or durability result.
Read the original reviewTest setup, measurements & limitations
Kakaku.com: WD4005FFBX as a hot-swap RAID6 spare in an HP NAS
Tested: One WD4005FFBX replacing a failed member in a company HP NAS RAID6; hot-swap; no format; Japan; enclosure model not stated. Author サイクロンエフェクト wrote it as a stopgap until a new NAS the following fiscal year (残り数ヶ月).
Applies to: Exact-MPN first-hand install story. Not a throughput, noise, durability or general NAS-compatibility result. The array was expected to be replaced in a few months.
- Bought as a generic-spec replacement after HP OEM 4TB pricing was described as over ¥100,000 and on-site support had expired.Source location: Review body, 2024-11-24 entry 1906010-1 by サイクロンエフェクト
- Hot-swap: old drive removed, carrier reused, array rebuilt without formatting.Source location: Review body ホットスワップ paragraph
- Explicitly a short-term stopgap: a new NAS was expected the next fiscal year, so this drive was to keep the array alive for the remaining months. RAID6 still had one more failure of spare.Source location: 来年度には新NASが来る予定なので、残り数ヶ月の命をつなぐためでした
Limits to keep in mind
- One user, unnamed HP NAS, Japan retail, no measurement tools.
- Stopgap until a replacement NAS; not evidence of long service life or broad compatibility.
- Kakaku star table omitted here; those scores have no method.
- Username tooltip defines モニタレビュー in general; this review is counted in the ordinary 満足度 aggregate (1 ordinary review). Gift/loan still unknown, not false.
Before you buy
Dated WD4005FFBX prices and ownership costs
Newegg 2026-09-11
Sold and shipped by Newegg at $244.99, in stock, limit 2 observed. Same dollar amount as the 2026-09-08 historical row; this is a new open, not an edited timestamp.[3]
B&H 2026-09-08, blocked 2026-09-11
Historical $286.99 in-stock observation. Cloudflare challenge on revisit.[4]
Amazon ASIN B0D1V6F7Y9
Exact-MPN detail page with no qualified new buy box on 2026-09-11.[6]
Compare stores for this exact model
One retail 4TB 3.5-inch SATA WD4005FFBX. Enclosure, extra drives and RAID are separate. Check the total delivered price at the store.
Lowest observed price
$254.18
Stock not confirmed
No currently purchasable offer recorded
Currency not confirmed
5 stores · 1 recent price observation
Amazon
Sold by Amazon.com
$254.18
Observed price
Currency not confirmed
Stock not confirmed · Condition not recorded
Observed Oct 9, 2026, 4:01:40 AM UTC[12]
View exact product at AmazonNewegg
Sold by Newegg
$244.99
Historical price
Stock not confirmed · New
One 4 TB WD4005FFBX 3.5-inch SATA internal NAS HDD, bare drive
Observed shipping: $0.99
Observed Oct 5, 2026, 2:09:41 AM UTC[10]
View exact product at NeweggB&H
Sold by B&H Photo Video
$286.99
Historical price
Stock not confirmed · New
One 4 TB WD4005FFBX 3.5-inch SATA internal NAS HDD
Check delivery availability and final shipping cost for your address. Historical price. Re-open before treating as a live offer.
Observed Sep 8, 2026, 3:49:13 PM UTC[4]
View exact product at B&HWestern Digital
Seller not recorded
$299.99
Historical price
Currency not confirmed
Stock not confirmed · Condition not recorded
Observed Sep 26, 2026, 4:08:04 PM UTC[11]
View exact product at Western DigitalMemoryC
Seller not recorded
Check price
Stock not confirmed · Condition not recorded
Observed Date not confirmed
View exact product at MemoryCPrices are dated observations. Confirm the model, seller, condition, stock and delivered total at the store. Older prices remain visible as history. Links may earn a commission.
CMR, store vs data sheet, and compatibility
Is WD4005FFBX CMR?
Yes. The January 2025 data sheet column and the US store specification block both say CMR.[1][2]
Why does the WD store say 217 MB/s if the data sheet says 267 MB/s?
Those figures come from different official surfaces on 2026-09-11. 267 MB/s is the WD4005FFBX table cell (footnote 3). 217 MB/s is what the store specification block prints for this SKU and matches the older WD4003FFBX column. Do not average them; confirm which document your seller is using.[1][2]
Does unlimited bays mean it is certified in my NAS?
No. That is family marketing. You still need the enclosure vendor’s exact-MPN list and firmware policy.[1][2]
Will it replace a failed drive without reformatting?
One Kakaku user did a hot-swap into an HP NAS RAID6 and the array rebuilt without a format. That is a single configuration, not a guarantee for every controller.[7]
Does RAID replace a backup?
No. RAID is availability. Keep an independent backup.[1]
Sources
Research updated Sep 11, 2026. Individual source check dates are listed below. Measurements belong to the named reviewers; tested configurations and software versions may differ from the product you buy.
- [1] Western Digital WD Red Pro datasheet (January 2025) ↗
Checked Sep 11, 2026 · Page 4 WD4005FFBX column plus footnotes 1–8 and page 1 unlimited-bays highlight
- [2] WD US store: 4TB WD Red Pro WD4005FFBX ↗
Checked Sep 11, 2026 · Selected 4TB variant; Specifications block; Key Features; Disclosures 1–4
- [3] Newegg WD4005FFBX product listing ↗
Checked Sep 11, 2026 · H1/pn WD4005FFBX; Sold by Newegg; $244.99; Instock true
- [4] B&H WD4005FFBX product listing ↗
Checked Sep 11, 2026 · Historical 2026-09-08 observation; 2026-09-11 Cloudflare challenge
- [5] Western Digital WD4005FFBX product listing ↗
Checked Sep 11, 2026 · Manufacturer PDP; price/inventory remain unresolved templates
- [6] Amazon WD4005FFBX detail page B0D1V6F7Y9 ↗
Checked Sep 11, 2026 · Title WD4005FFBX; unqualifiedBuyBox; no selected new main offer
- [7] Kakaku.com user review 1906010 of WD4005FFBX ↗
Checked Sep 11, 2026 · Review 2024-11-24; RAID6 HP NAS hot-swap narrative
- [8] Nero Score user results for WDC WD4005FFBX-68CAUN0 ↗
Checked Sep 11, 2026 · User-submitted sequential 254/253 MB/s; first-seen date 08/2021 is inconsistent with this SKU
- [9] Western Digital warranty policy ↗
Checked Sep 11, 2026 · Region-specific limited warranty details linked from data sheet footnote 7 / store disclosure 4
- [10] Newegg product price observation ↗
Checked Oct 5, 2026 · newegg-main-item; sha256:9c535826169a53b1f59da5de2a439de851e6bcccc6affd72eba57bdd65982e4f
- [11] Western Digital product price observation ↗
Checked Sep 26, 2026 · Captured observation; sha256:a0c2a31b3405d138ac76c94e1baa91b1bfa29b391b6c4c59e322242d9776a7f1
- [12] Amazon product price observation ↗
Checked Oct 9, 2026 · Captured observation; sha256:c47b18238364386de7257a553cc93b05ee4b1bbc27042728c8788e72fbe3acf9
Research and review record
- Research: Grok 4.6 · Source research and data update
- Self-check: Grok 4.6 · Researcher self-check
- Independent review: GPT-6 (Codex) · Exact Jan2025 WD Red Pro4/6/8TB columns and footnotes, conflicting official store values, exact current merchant primary offers and dated historical rows; bounded Kakaku user experience for4TB. No exact-MPN lab benchmark claimed; gaps and index decisions preserved.
- Editorial integration: GPT-6 (Codex) · Editorial integration and validation
Independent review completed for the scope recorded in the audit.
Source evidence and review history (JSON)