How Western Digital SMR Drives Ruined My Storage PerformanceWhen I built my NAS system, I expected reliable performance and longevity from my Western Digital drives.
Initially, I ran four 2TB Western Digital Red NAS drives in a RAID 10 array and was happy with the performance. However, as my storage needs grew, I decided to upgrade to four 6TB WD Red NAS drives, expecting a proportional increase in capacity and performance. Instead, I was met with frustratingly slow speeds and unexpected bottlenecks.
The Unexpected Performance Drop
At first, I suspected my hardware setup was the issue. I initially used a Buffalo NAS bay, thinking its limited processing power could be the culprit. However, moving to different configurations, including a dedicated Linux server running mdraid, a Windows Server setup, and even investing in a hardware RAID card, yielded no significant improvements. No matter how much I optimized the software, file transfers were sluggish, and rebuilding the RAID array took an eternity. Something was seriously wrong.
Uncovering the Western Digital SMR Drive Controversy
In 2020, news broke that Western Digital had been using Shingled Magnetic Recording (SMR) in their NAS drive lineup without disclosing it. This was a major red flag - WD Red NAS drives were marketed as professional-grade storage solutions, yet WD had secretly swapped in an inferior recording technology.
I decided to investigate my own drives, running tests to determine their behaviour. To my shock, one of my 6TB WD Red drives was actually a relabelled WD Blue, using SMR technology instead of the Conventional Magnetic Recording (CMR) I had expected.
In fact the final results were even more shocking. Out of the four 6TB Western Digital RED drives I purchased from a respectable retailer ony ONE of the drives was a genuine WD Red with CMR technology. Since all the drives are well out of warranty, let alone returns window there is nothing I can do about this other than check and examine every single drive I buy from now on.
| Label Identification | Label Serial Number | Detected Identification | Detected Serial Number | Drive Type | CMR | SMR |
|---|---|---|---|---|---|---|
| WD60EFAX | WX62D304S50P | WD60EFAX | WX62D304S50P | WD Red | X | |
| WD60EFAX | WX62D30RDF0H | WD60EFAX | WX62D30RDF0H | WD Red | X | |
| WD60EFRX | WX21DA87C4AU | WD60EFRX | WX21DA87C4AU | WD Red | X | |
| WD60EFRX | WCC2E9LB5259 | WD60EZAZ | WX11D1951J7L | WD Blue | X |
I don't know if this WD Blue is part of the scandal involving WD Red Drives or if it was swapped out by some unscrupulous individuals somewhere along the supply chain, either way I paid for server quality drives and got inferior consumer drives which are totally unsuitable for my NAS.
SMR vs. CMR: Why It Matters
Hard drives store data on spinning disks called platters, which are coated with a magnetic material. These platters contain concentric circles known as tracks, which are further divided into sectors - the smallest addressable units of storage. A collection of sectors is grouped into clusters, which are used by the file system to store data efficiently.
When data is written to a hard drive, the read/write head moves across the spinning platters, magnetizing specific regions to represent binary data (0s and 1s). The efficiency of this process is crucial to overall drive performance, especially in RAID configurations where multiple drives work together.
Understanding the difference between SMR and CMR is crucial when dealing with RAID setups:
- CMR (Conventional Magnetic Recording) writes data in parallel tracks, allowing for fast, consistent read/write speeds. It is ideal for NAS, RAID, and other high-performance storage systems.
- SMR (Shingled Magnetic Recording) overlaps data tracks to increase density, but at the cost of performance. Writing new data requires rewriting large sections of the disk, causing massive slowdowns and making them unsuitable for RAID arrays.
Why SMR is Bad for RAID 10 and ZFS
RAID 10 and ZFS rely on predictable and consistent write speeds. When an SMR drive is introduced into the array, it becomes a bottleneck:
- RAID 10 writes data across multiple disks simultaneously - if one disk is slow due to SMR, the entire array slows down.
- Rebuilding a RAID array takes significantly longer with SMR drives, sometimes days instead of hours.
ZFS relies on fast sync writes, which SMR drives struggle with, leading to performance degradation and potential data integrity issues.
For a NAS setup, Western Digital SMR drives are completely unsuitable yet Western Digital knowingly sold them as NAS-grade hardware.
What is ZFS and How It's Used in NAS/RAID Arrays
ZFS (Zettabyte File System) is an advanced file system and volume manager designed for high-performance, high-reliability storage. Originally developed by Sun Microsystems, it is widely used in NAS systems due to its robust data protection features. Unlike traditional RAID, ZFS integrates RAID functionality at the filesystem level, providing benefits such as:
- Copy-on-Write (COW) which ensures that data is never overwritten in place, reducing the risk of corruption.
- Data Integrity Checksums which detect and corrects silent data corruption automatically.
- Self-Healing Mechanisms identify and repair corrupted data using redundant copies stored across the array.
- Supports massive storage capacities with built-in compression and deduplication features.
ZFS requires consistent, predictable write speeds to function efficiently. SMR drives disrupt this process by introducing slow, unpredictable write performance, leading to degraded NAS performance and potential data integrity risks. This makes SMR drives a terrible choice for ZFS-based NAS solutions, as they can significantly slow down read/write operations and increase rebuild times in the event of drive failure.
For a NAS setup, SMR drives are completely unsuitable - yet Western Digital knowingly sold them as NAS-grade hardware.
No Fix, No Refund, No Trust
Since I purchased my drives in 2018, the return period had long expired by the time I discovered the deception. There was nothing I could do to fix the issue because it was a hardware limitation. My only options were to live with slow performance or replace the drives at my own expense.
Western Digital's decision to silently slip SMR drives into their NAS lineup felt like a betrayal. The storage community erupted in anger, with countless other users facing similar problems. Eventually, due to public backlash, WD was forced to acknowledge the issue and clarify which of their drives used SMR, but by then, the damage was done.
Boycotting Western Digital
The way WD handled this situation left a lasting impression - not just on me, but on the entire storage community. As a long time user of Western Digital drives I have vowed never to buy another Western Digital drive again, and many others have done the same. The company prioritized cost-cutting over customer trust, and in an industry where data integrity is everything, that's unforgivable.
If you're building a NAS or RAID system, avoid Western Digital SMR drives at all costs. Always verify that your drives use CMR technology before purchasing. And if a company has already betrayed your trust once - think twice before giving them another chance.
