ST4000DM004 Seagate BarraCuda 4TB: SMR and Why Not for NAS
The ST4000DM004 is a Seagate BarraCuda 4TB desktop drive, and at 4TB it looks like a cheap way to fill a NAS. It is not. This covers what it is, the specific reason it fails in arrays, and what to buy instead.
What is the Seagate ST4000DM004?
A 3.5 inch, 4TB, SATA 6Gb/s desktop hard drive from the BarraCuda family. 5400 RPM class, and critically, shingled magnetic recording (SMR).
At 4TB it is one of the cheapest drives per terabyte available, which is exactly why it ends up in NAS units and RAID arrays where it should not be.
Why does SMR matter at 4TB?
Because the failure appears during a rebuild, months after purchase.
SMR overlaps tracks to fit more data per platter. Rewriting one track means rewriting the tracks that overlap it, which the drive handles internally and slowly. Sequential writes are fine; random writes collapse once the drive’s internal buffer fills.
A RAID rebuild is a sustained heavy write to the new drive. On an SMR drive that can slow to a fraction of normal speed for hours or days, and the controller may decide the drive has failed and drop it. Our SMR vs CMR guide covers the mechanism in full.
The array works perfectly until the day you need it to rebuild. That is the worst possible failure timing.
Is the ST4000DM004 usable at all?
Yes, in the role it was designed for.
Single-drive bulk storage in a desktop or workstation, where files are written once and read many times.
External USB storage for media libraries and archives.
Cold backup targets receiving large sequential writes, provided the backup software does not do random writes for indexing.
In those roles it delivers 4TB cheaply and works fine.
What to buy for a NAS or server at 4TB
NAS: Seagate IronWolf 4TB or WD Red Plus, confirmed CMR. Our drive class guide covers what NAS drives add.
Server or array: Seagate Exos 7E8 4TB, Toshiba MG series, or WD Ultrastar. Our Exos 7E8 4TB guide covers the enterprise option at exactly this capacity, and it is CMR.
The price difference is real but smaller than people expect, and it buys you an array that rebuilds.
How do I check what I already have?
Read the exact model number from each drive, then check it against the manufacturer’s published SMR/CMR list. The label on the drive and the operating system both report the model. Our drive health guide covers querying drives.
If you find SMR drives in an array, replace them with CMR before the next rebuild, one at a time, allowing each rebuild to complete.
Frequently asked questions
Is the ST4000DM004 SMR?
Yes. It is a shingled magnetic recording desktop drive, which is why it is among the cheapest 4TB drives per terabyte.
Can I use the ST4000DM004 in a NAS?
No. Random writes collapse once the buffer fills, and a RAID rebuild can slow so much that the controller drops the drive as failed. The array works until the day it needs to rebuild.
What is the ST4000DM004 good for?
Single-drive bulk storage, external USB media libraries, and cold backup targets receiving large sequential writes. In those roles it delivers 4TB cheaply and works fine.
What 4TB drive should I buy for a NAS?
A CMR NAS-class drive such as IronWolf or WD Red Plus. For a server or array, an enterprise nearline drive such as the Exos 7E8 4TB.
How do I check if my drives are SMR?
Read the exact model number from each drive and check it against the manufacturer’s published SMR/CMR list. It is rarely printed on the label as SMR.
I have SMR drives in my array. What now?
Replace them with CMR before the next rebuild, one at a time, allowing each rebuild to complete before starting the next.
Tell us the NAS or server and the capacity you need, and we will quote a CMR drive that will actually rebuild when you need it to.
