WD Red Pro 24TB Review: CMR, 550TB a Year, and Rebuild Time

Updated 2026-08-21 Researched, not tested in person Vendor neutral

Quick answer

Twenty four terabytes of 7200 RPM CMR storage rated for 550TB per year and up to 2.5 million hours MTBF, with no bay-count limit. Buy it if you want maximum capacity per bay in a NAS built for continuous operation. Understand before you do that a drive this large takes a long time to rebuild after a failure, and that a long rebuild on a single-parity array is exactly when a second drive is most likely to fail.

The capacity that makes a four-bay hold what an eight-bay used to, and the rebuild window that comes with it.

Highest Capacity Per Bay

Western Digital 24TB Red Pro NAS Internal Hard Drive, 7200 RPM, SATA 6 Gb/s, CMR

~$1,060

A 7200 RPM CMR NAS drive rated for RAID-optimised systems with unlimited bays, 550TB per year workloads and continuous operation.

Check price on Amazon

Specifications

Capacity	24 TB, with the family running 2 TB to 26 TB
Speed	7200 RPM
Recording	CMR, conventional magnetic recording
Interface	SATA 6 Gb/s
Bays	Rated for RAID-optimised NAS with an unlimited number of bays
Workload	Rated for 550 TB per year
MTBF	Up to 2.5 million hours
Duty	Designed for continuous operation

Specifications above come from Western Digital's published specifications. Treat pricing as approximate, since Amazon pricing moves.

What it does well

CMR rather than SMR, which is the single most important specification in a NAS drive. SMR drives can slow to a crawl during a RAID rebuild, and that is the worst possible moment for it.
No bay-count limit, unlike the Red Plus family which is rated for up to eight bays. In a large array that matters.
A 550TB per year workload rating is enterprise territory and covers anything a home server will do many times over.
Twenty four terabytes per bay means a four-bay unit can hold what used to need eight, with a quarter of the drives spinning, drawing power and making noise.
Rotational vibration handling and 7200 RPM performance are what separate a NAS drive from a desktop drive in a dense chassis.

Where it falls short

Rebuild time is the real cost of large drives. Rebuilding a 24TB drive into an array takes many hours and often more than a day, and the array is degraded and working hard for that entire window.
That rebuild window is the argument for double parity. On single-parity RAID 5 or SHR-1, a second failure during a 24TB rebuild loses the array, and the probability is not negligible.
Seven thousand two hundred RPM drives are louder and hotter than 5400 class drives. Four of these in a chassis is audible.
The price per terabyte is not the best in the range. Mid-capacity drives are usually better value per terabyte; you are paying for density per bay.
Larger drives mean larger single points of loss. Losing one drive is losing 24TB of your redundancy budget at once.

What owners report

Owner reports on Red Pro drives are consistent and unremarkable, which is what you want from a hard drive. The recurring theme in the wider NAS community is not about this drive but about drive size in general: as capacities grow, rebuild windows grow with them, and single parity becomes harder to justify.

Our RAID 5 versus RAID 6 comparison is the piece to read alongside any drive this large, and the rebuild time chart puts hours on the window. The drive failure probability calculator estimates the risk of a second failure during that window, which is the number that should decide your RAID level.

On CMR against SMR, our drive selection guide covers why it matters and how to check. It is the specification that most often gets people into trouble, because SMR drives are sold without prominence given to the recording method and they behave acceptably until the day you need a rebuild.

Who it suits

Four-bay and larger arrays wanting maximum capacity per bay.
Anyone running double parity, where large drives are safe to use.
Builds where reducing the number of spinning drives matters for power and noise.

Who should skip it

Single-parity arrays, where a 24TB rebuild window is a real risk.
Buyers optimising cost per terabyte, where mid-capacity drives are usually better value.
Quiet rooms, since four 7200 RPM drives are audible.

Alternatives worth considering

Shorter Rebuilds

Seagate IronWolf Pro 16 TB Enterprise NAS Internal HDD, CMR, 7200 RPM

~$580

Sixteen terabytes of CMR with the same 550TB per year workload rating and a five-year warranty, plus three years of Rescue data recovery included. Smaller capacity means a meaningfully shorter rebuild window.

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Cheaper Per Bay

Western Digital 12TB Red Plus NAS Internal Hard Drive, 7200 RPM, CMR

~$460

CMR, NASware firmware and a 180TB per year workload rating, for up to eight bays. Less workload headroom and a lower price. The bay limit is the thing to check against your chassis.

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Enterprise Class

Seagate 20TB Exos Enterprise Hard Drive, SATA

~$800

A data centre drive with a 2.5 million hour MTBF and a five-year warranty at a lower price per terabyte than consumer NAS drives. Enterprise drives are typically louder and draw more power, which is the trade for the price.

Check price on Amazon

Keep reading

This review draws on published specifications, manufacturer figures and the consensus of verified owner reviews. We have not tested this product ourselves, and we say so rather than implying otherwise. As an Amazon Associate we earn from qualifying purchases.

Frequently asked questions

What is CMR and why does it matter for a NAS?

Conventional magnetic recording writes tracks side by side. Shingled recording overlaps them, which raises density and makes rewriting slow, because overlapping tracks must be rewritten together. In a NAS that shows up during a RAID rebuild, where an SMR drive can slow dramatically at precisely the moment the array is vulnerable. Always confirm a NAS drive is CMR.

How long does a 24TB drive take to rebuild?

Many hours and often more than a day, depending on the array, the RAID level and how busy the NAS is. The array runs degraded and under heavy load for the whole window, which is why very large drives push most people toward double parity. Our rebuild time chart gives estimates by capacity.

Should I use RAID 5 with 24TB drives?

Most experienced administrators would not. Single parity survives one failure, and a multi-day rebuild across drives of the same age and batch is when a second failure is most likely. RAID 6 or SHR-2 survives two, at the cost of one more drive of capacity. Our RAID 5 versus RAID 6 comparison covers the trade.

Red Pro or Red Plus?

Red Pro is 7200 RPM, rated for 550TB per year and for an unlimited number of bays. Red Plus is rated for 180TB per year and for up to eight bays. For a four-bay home NAS, Red Plus is usually enough and costs less. For larger arrays or heavier use, Red Pro is the correct part.

Do I need to burn in a new drive?

It is worth doing. Drive failures cluster early, and finding a bad drive before it holds your data is far better than finding it during a rebuild. Our drive burn-in testing guide covers a sensible routine before you commit an array to a new set of disks.

How we choose: we compare published manufacturer specifications, drive datasheets, published reliability statistics and verified owner reviews. We do not test hardware in person, and we are not tied to any NAS vendor. Capacity and power figures here are researched guidance, not a warranty. RAID protects against drive failure, not against deletion, ransomware, fire or theft, so keep verified backups regardless of what any calculator tells you.

Working out your own cost per usable terabyte? The Home Server Build Planner is the paid version of these pages: 8 printable worksheets you fill in with your own numbers, plus the full PDF, $29.