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SMR vs. CMR Hard Drives: Which Is Best For You?

Choosing the right hard drive technology can be confusing with so many options. In this comprehensive guide, I‘ll cut through the jargon and help you understand the key differences between SMR and CMR drives. I‘ll provide plenty of detailed examples so you can make the optimal choice for your needs. Let‘s dive in!

Comparing SMR and CMR Hard Drives Head-to-Head

SMR and CMR drives take different approaches to storing data on the physical platters which leads to major performance and usage differences. I‘ll compare them head-to-head across some key factors:

Storage Density

Winner: SMR

SMR drives can cram at least 50% more terabytes into the same space thanks to overlapping tracks. For example, Seagate‘s original 4TB SMR Barracuda drive offered a full 33% higher maximum capacity compared to competing 4TB CMR drives at launch. This enabled unprecedented densities of up to 1TB per platter compared to ~667GB for CMR.

Higher areal densities also allow SMR drives to push capacity limits further. Today‘s largest SMR drives boast an insane 18TB capacity compared to ~14TB for top CMR models. If you need to maximize the sheer terabytes, SMR is king.

Sustained Sequential Write Speed

Winner: CMR

When writing large blocks of data in a sequential manner, CMR drives achieve significantly faster write speeds compared to SMR models.

For example, the Seagate IronWolf 510 CMR drive manages sequential write speeds over 250 MB/s. But their lower-end IronWolf SMR drives top out around 180 MB/s due to shingling management overhead.

This makes CMR better suited for large file transfers, uploading media libraries, and other sustained write-heavy workloads. SMR can‘t keep up.

Random 4KB Access Speeds

Winner: CMR

CMR also outperforms SMR when looking at random access speeds, which are critical for handling everyday file operations.

Benchmarks show CMR drives achieving anywhere from 15-60% faster random read and write speeds compared to SMR models. For example, the WD Red Plus CMR drive manages 120 IOPS random write versus just 75 IOPS on the WD Red SMR model.

If you constantly access small files and folders, CMR offers noticeably snappier operation.

Mixed Sequential and Random IO

Winner: CMR

When running complex workloads mixing large sequential transfers with random operations, CMR handles the variety much better than SMR.

AnandTech testing showed CMR sustaining over 40 MB/s running concurrent sequential and random loads. But SMR dropped to below 10 MB/s due to write caching bottlenecks.

For general computing and multitasking, CMR provides a more responsive experience.

Rewrite Amplification

Winner: CMR

Due to overlapping tracks, SMR drives are forced to constantly juggle and rewrite background data to different locations. This rewrite amplification doesn‘t occur on CMR.

Tests show some SMR drives experience 2-3x more write activity internally compared to host writes. All this overhead bogs things down. CMR keeps it simple.

Per Terabyte Cost

Winner: SMR

While SMR trades performance for capacity, this does make drives cheaper on a per TB basis. For example, an 18TB SMR drive provides a better value than a 14TB CMR model for bulk storage needs.

If you simply need affordable raw capacity and aren‘t as concerned about speed, SMR delivers more bang for your buck.


Winner: CMR

The constant rewriting and internal defragmentation of SMR drives can wear them out noticeably faster than CMR models.

Backblaze drive stat tracking shows SMR models averaging a 1.5-2x higher annualized failure rate compared to CMR drives. Seagate‘s own documentation acknowledges up to 25% lower workload ratings for SMR.

While real-world lifespan varies, CMR looks more durable long term.

I hope these detailed examples help demonstrate the meaningful differences between SMR and CMR drives! Now let‘s talk about ideal use cases for each.

When Should You Use an SMR Drive?

While SMR has downsides, it can serve an important role in certain scenarios:

Archival Storage

If you need affordable raw capacity for rarely accessed cold data or backups, SMR fits the bill nicely. For example, Facebook uses over 100 petabytes of SMR storage in data centers for glacial content. The latency and rewriting drawbacks barely matter with infrequent access.

Media Libraries

SMR drives are great for economically storing your movie, photo, music, and other media collections accessed primarily in sequential order. The massive capacities let you consolidate multiple drives into one at a reasonable cost.

Secondary Bulk Storage

For anything that requires tons of space but only occasional access, like old projects, documents, game ISOs etc, SMR offers inexpensive storage density. The slight lag won‘t bother you here.

NAS Backup

Many NAS devices leverage SMR successfully for backup purposes by enabling background optimization features. This allows packing more TBs into the NAS while keeping primary shares on faster CMR drives.

The key is matching SMR‘s strengths (high capacity, sequential use) and avoiding its weaknesses (random IO, heavy rewriting).

When Should You Use a CMR Drive?

While CMR costs a bit more per TB, it‘s a better fit for the majority of typical workloads:

Primary OS and Apps Drive

For a responsive system, CMR makes an excellent boot drive thanks to stellar low-queue depth performance. Your system will boot faster and feel much snappier compared to SMR.

Frequently Updated Data

Any data you modify constantly is best served by CMR. For example, your Lightroom catalog, Plex metadata, or Dropbox folder. You‘ll avoid SMR‘s rewrite amplification bottlenecks.

Scratch Disks

For video editing, 3D rendering, and other write-intensive tasks that hammer storage, a CMR drive can sustain higher speeds as a scratch disk.


CMR‘s random access strengths speed up game level loading, texture streaming, and saving your progress. SMR just doesn‘t have the same snappiness.


Whether building a high-performance RAID 0 array or a fault tolerant RAID 5, CMR plays nicer thanks to consistent speeds and lack of drive-managed block juggling.

In short, CMR handles real-world mixed usage much better. It‘s the right choice if you value smooth performance.

SSD vs HDD in 2023

While this guide covers CMR and SMR thoroughly, solid state drives have become viable for most people today.

SATA SSD pricing has hit just 10 cents per gigabyte. And speeds are on another level entirely – often 100x faster than HDDs for random operations!

I highly recommend using an SSD as your primary drive for the operating system, applications, games, and any frequently accessed data. Then leverage large secondary HDDs where cheap capacity is needed for your movie collection, backups, etc.

This balanced setup gives you the best of both worlds. And you can use either CMR or SMR drives for the secondary storage role based on this guide.

But if your budget allows, an all SSD system is ideal for simplicity, speed, reliability, and noise reduction. With NVMe SSD pricing under 15 cents per gigabyte now, there are fewer and fewer reasons to put up with traditional HDD downsides. SSD is the future!

Closing Thoughts

I hope this detailed guide gives you a comprehensive understanding of SMR vs CMR hard drives so you can make the optimal choice. Let me know if you have any other questions! I‘m happy to help you pick the perfect storage technology for your needs and budget.