Still scaling with CMR? See why more organisations are evaluating UltraSMR.
The Ultrastar DC HC6100 with WD UltraSMR technology delivers up to 34TB in the existing 3.5" form factor, helping data centers maximise storage density, improve power efficiency and optimise total cost of ownership (TCO) for AI-driven workloads.
For cloud, hosting and AI infrastructure providers, this page sets WD's published figures side by side: the 28TB Ultrastar DC HC5090 (CMR) and the 34TB Ultrastar DC HC6100 (UltraSMR).
UltraSMR vs CMR, same HDD generation
18%
more capacity · 4TB per HDD
UltraSMR extends the capacity advantage to two HDD generations before the same capacity is available in CMR.
Source: WD UltraSMR Tech Brief, July 2026
CMR and UltraSMR, side by side
Both drives are 3.5" helium data center HDDs with 7,200 RPM spindles, 512MB cache, 24x7 availability, a projected AFR as low as 0.35% and a 5-year limited warranty. The differences are in capacity, density, throughput and power.
| CMRUltrastar® DC HC5090 | UltraSMRUltrastar® DC HC6100 | |
|---|---|---|
| Capacity | 28TB | 34TB |
| Recording technology | CMR | SMR, UltraSMR recording format |
| Areal density | 1,285 Gbits/sq. in. | 1,560 Gbits/sq. in. |
| Interface | SATA 6Gb/s or SAS 12Gb/s | SATA 6Gb/s |
| Sustained transfer rate (max) | 308 MB/s (294 MiB/s) | 273 MB/s (260 MiB/s) |
| Idle power (SATA) | 5.5 W | 5.4 W |
| Idle power efficiency | As low as 0.20 W/TB (SATA) | As low as 0.16 W/TB |
| Random read 4KB QD=8 at max IOPS (SATA) | 9.2 W | 8.1 W |
| Workload rating | 550TB/year | 550TB/year |
| Warranty | 5-year limited | 5-year limited |
Specifications as published in the WD Ultrastar DC HC5090 and DC HC6100 data sheets. Capacity in decimal units (1 TB = 1 trillion bytes); actual user capacity may be lower. Sustained transfer rates are maximums based on internal testing and vary by host, capacity and LBA. AFR values are projected, not a prediction for an individual drive and not a warranty. Idle figures use the Idle_A profile. Product specifications are subject to change.
What makes UltraSMR different
UltraSMR is a collection of hardware, controller and read channel technologies that expand the capacity advantage SMR has over CMR. WD's tech brief names four building blocks.
Read heads
Two-dimensional magnetic recording
A second read head filters out off-track noise, so shingled tracks can overlap to a larger extent, increasing tracks per inch.
Sector format
Distributed sectors
Data from multiple sectors is interleaved over a wider area, so a local defect damages only a small part of many sectors instead of one sector.
Error correction
Soft-decoded track ECC
Likelihood analysis lets a single parity sector correct multiple uncorrectable sectors, improving error correction efficiency by an order of magnitude or more.
Enabler
OptiNAND™
Embedded iNAND® flash holds the transient data UltraSMR needs, retaining it if power is lost before it is committed to the media.
Where each drive fits
CMR
Ultrastar® DC HC5090
Field-proven CMR technology delivers predictable performance for diverse data environments, designed for high-throughput, sequential and mixed workloads.
- AI pipeline data sets
- AI checkpoint and log files
- Warm data storage and data lakes
- Content libraries
UltraSMR
Ultrastar® DC HC6100
High density storage up to 34TB at optimised TCO for warm and cool data center workloads, where capacity matters most.
- AI training data sets and pipeline checkpointing
- Data lakes and content libraries
- Compliance and regulatory data
- Backup and archival data sets
- Warm and cool data storage tiers
Why the economics are shifting
Every drive in the data center needs power, generates heat that needs cooling, takes up physical volume and a chassis slot, and must be supported by host bus adapter port bandwidth. WD's tech brief calls this the "slot tax".
TCO is generally measured in $/TB, W/TB, TB/in³ and TB/slot, so increasing capacity per drive typically reduces TCO. With UltraSMR, WD says large customers can now justify the software investments needed to deploy Zoned Storage HDDs.
What the transition involves
UltraSMR builds on shingled magnetic recording, which overlaps the physical tracks on the media during write operations.
Per WD's tech brief, exploiting the capacity advantage of host-managed SMR requires software changes. Talk to us early so your team can scope that work against the capacity and TCO gains.
Looking at the platform layer?
WD's Ultrastar Data60 and Data102 hybrid storage platforms support dual-port SAS drives for high availability or single-port SATA for low cost. Talk to us about the right drive and platform combination for your deployment.
Ultrastar® Data60
- 24 to 60 drives
- Up to 1.92PB
- Up to 12 x 12Gb/s SAS-3 host connections
- 5-year limited warranty
Ultrastar® Data102
- 60 to 102 drives
- Up to 3.26PB
- Up to 12 x 12Gb/s SAS-3 host connections
- 5-year limited warranty
Integrated solution
Need an integrated storage infrastructure solution?
Our sister company, Circle B, offers Build-to-Order for customers who require an integrated storage infrastructure solution.
Available through Taurus Europe
Taurus Europe supplies enterprise storage solutions for modern IT infrastructure, cloud platforms, AI environments, and data-intensive workloads. With access to leading enterprise component manufacturers, we help customers source reliable, high-capacity storage for current and future infrastructure requirements.
Speak with our team about the Ultrastar DC HC6100 and DC HC5090, the Data60 and Data102 platforms, and how to plan the transition from CMR to UltraSMR.
Product / Availability
ManufacturerWD
UltraSMR driveUltrastar DC HC6100
CMR driveUltrastar DC HC5090
PlatformsUltrastar Data60 / Data102
Integrated optionCircle B Build-to-Order
SupplierTaurus Europe
RegionEurope
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