Hey there! As our appetite for storing everything digitally continues to balloon year over year, choosing the right storage technology for all those petabytes of movies, music, photos and work files is more critical than ever. For mass storage, hard disk drives remain the most cost-effective solution. But there are two main types of HDDs to choose between — conventional magnetic recording (CMR) and the newer shingled magnetic recording (SMR) approach.
Each offer a distinct set of advantages and limitations when it comes to factors like speed, max capacity, lifespan, and overall value. In this comprehensive guide, we’ll dig into the key differences between CMR vs SMR, when each method makes sense based on your needs, and what the future holds in the never-ending quest for more efficient data storage. Let’s have some fun exploring the world of hard drive guts!
History of CMR and SMR Technology
Conventional magnetic recording has been used in HDDs for over 50 years. This method lays down circular tracks of magnetically encoded data across spinning platter surfaces inside hard disk enclosures. Hundreds of thousands of tracks comprising individual bits are neatly arranged side-by-side with defined borders thanks to precise actuator arms.
This approach easily allows any track to to be rewritten without affecting adjacent tracks. Performance remains consistent even as the drive fills up during use. But the laws of physics imposed limitations on how narrowly tracks could be stacked. There was minimal room left to expand storage capacities as our data grew exponentially throughout the 2000s.
Enter shingled magnetic recording pioneered by Seagate engineers in 2009. This technology layers new tracks partially over the edge of existing tracks in an overlapping shingle-like pattern to maximize every nanometer of platter real estate. This boosted aerial density a remarkable 25-50% over CMR! Seagate shipped the world‘s first SMR drive in 2013 cramming an incredible 5TB into a single unit.
But this extreme density comes at a cost — slower write performance, shorter working lifespans for drives, and more complexity for manufacturers and host devices to ensure stability. Now 10 years into mainstream SMR adoption, we can quantify differences and help match use cases to the optimal tech.
| Specification | CMR | SMR |
|---|---|---|
| Date Introduced | 1956 | 2009 |
| Aerial Density | ~750 Gbit/in2 | 1000+ Gbit/in2 |
| Max Capacity Per Drive | 16TB | 20TB+ |
| Read/Write Performance | Up to 260MB/s | Avg 100-150MB/s |
| Drive Lifespan | 5-7 years | 2-4 years |
Diving Into the Technical Details
To better understand the core difference between conventional vs shingled magnetic recording methods used in HDDs, we need to quickly geek out on some underlying principles…
Hard disk drives store our precious data on quickly spinning metal platters coated in magnetic recording material. Read/write heads float nanometers above these platter surfaces on actuactor arms reaching up to dual-actuator speeds. These heads alter the magnetic orientation of tiny grains on the drive media to write new data and detect polarity changes to read back the encoded data.
The density equation = tracks per inch (TPI) * bits per inch (BPI) summed across all platters in the hard drive enclosure. Conventional drives lay down tracks packed tightly together but still separated by defined guard bands running the circumference of platters. This allows random rewrites without affecting adjacent tracks. SMR overlaps tracks like shingles on a roof to eliminate guard band spacing nearly doubling total tracks per inch.
The next diagram demonstrates the layout differences:
This trick works brilliantly to increase areal density but requires intelligent write caching and track management to prevent stray magnetic charges from corrupting adjacent shingled tracks during rewrites.
Now that we understand how SMR achieved such radical density improvements vs CMR, let’s explore how it impacts real world performance, lifespan, and total cost of ownership depending on your use case.
Comparing Read/Write Speeds
Our first test metric is sustain read/write throughput measured in megabytes per second (MB/s). Faster is better whether we‘re loading game levels or updating catalogs of photos.
Benchmarking testing from sites like Tom‘s Hardware and StorageReview reveal noticeable speed advantages for CMR drives over SMR equivalents. Lets take the popular WD Red series as an example comparing the CMR-based WD Red Pro models against shingled WD Red drives.
{| class="wikitable"
|-
! Drive Model !! CMR/SMR !! Avg Sustained Write !! Avg Sustained Read
|-
| WD Red Pro 8TB || CMR || 205.5 MB/s || 249.3 MB/s
|-
| WD Red 8TB || SMR || 147.0 MB/s || 191.0 MB/s
|}
You‘ll notice about 30% faster writes and 20% quicker reads favoring the conventional magnetic recording design even though thousands less tracks are packed onto each spinning platter. Why doesn’t overlapping more tracks provide a density dividend?
The reason is something called write amplification. Because new SMR writes can unintentionally alter data in overlapping tracks, a whole sequence of read, save to cache, erase, rewrite must happen to prevent corruption. Manufacturer firmware maximizes sequential write streams and caches data during idle periods to complete commits. Workloads mixing random access writes fare even worse.
What does this mean for real world usage? Gamers, video editors and IT admins will enjoy snappier response loading levels or scrubbing through 4K footage on CMR external drives. Meanwhile home media hoarders slowly expanding their Plex libraries over time can still benefit from the extreme SMR capacities. For read-intensive applications the speeds narrow to within 10-20%.
Now let’s explore longevity…
Expected Working Life and Reliability
All spinning drives eventually fail — it’s only a matter of when and how gracefully they fade away. Modern HDDs primarily fall victim to one nemesis stronger than all others…the mechanical stress of nonstop spinning decade after decade. Fans pull in dust and humidity triggering corrosion over years. Heads cling closer to media barely the width of an atom but eventually crash or get thrown off track. Electrical components degrade over time.
These factors impact conventional and shingled drives but SMR workload intensity accelerates wear on multiple fronts thanks to the constant caching, idle commits and near continual overlapping writes. Cloud backup provider Backblaze quantifies the difference based on studying tens of thousands of disks in datacenter storage pods.
Across matched 4TB drive models they found CMR reliability averaging between 0.5-1% failure rates per year over 5+ years of service. By contrast SMR models displayed rising risk profiles nearing 2% by years 2-3 as mechanical stress added up. Thats 4X more likely to suffer catastrophc data loss outside of warranty coverage windows!
Even accounting for heavy 24/7 enterprise workloads, thats a stark lifetime difference likely exacerbated among portable external drives subjected to transportation shock and vibration. Definitely consider shelling out a few extra bucks for 3-5 year extended protection plans on SMR models providing backup storage.
Data Integrity and Correctability
While dramatic headline failures catch our attention, there exists a second kind of data adversity called bit rot or bitflip. As magnetic charges weaken over time, some become unreadable throwing checksums off and introducing possible corruption. Other stray magnetic noise can alter polarity states of bits along track paths.
Thankfully modern drives augment underlying storage with extensive error correction capabilities from on-the-fly ECC routines all the way up to specialized LDPC dual-actuators in high end enterprise gear. However the simpler, more elegantly laid out track boundaries of CMR media again prove slightly more resistant to stray charge interference as drives age.
Large scale cloud providers actually tweak software logic on hosts and internal networks with SMR knowledge to prevent edge case data integrity issues bubbling up to users. For home office use both technologies largely deliver missing bit immunity and self-healing. Best practices around scheduled scrubs and verified backups reign supreme.
Our next topic shifts from technical to practical – comparing value per terabyte and overall TCO…
Pricing per TB Across CMR and SMR Hard Drives
As data wranglers ourselves, we love maximizing capacity without breaking budget. Industry consolidation has unfortunately raised prices the last few years but robust competition keeps things reasonable. What savings does SMR extra density provide?
Running some real world examples with popular external HDDs shows a 10-20% discount per TB on SMR models at equivalent capacities. Right now on sites like Amazon and NewEgg the street pricing difference looks like:
-
4TB 2.5" Portable
- Toshiba Canvio Advance CMR = $85
- WD MyPassport SMR = $75
-
8TB 3.5" Desktop
- Seagate Backup Hub CMR = $149
- WD Elements SMR = $124
-
16TB 3.5" Desktop
- WD Easystore CMR = $309
- WD Elements SMR = $254
So expect to pay around $15 per TB on quality SMR drives and $18-20 per TB for CMR external hard drives at respective company’s highest density offerings. Of course sales can change the math further in your favor!
Factoring in the shorter predicted lifespan of SMR models definitely shifts value proposition towards conventional recording formats for drives storing original or actively edited data. But for gradually expanding media archives, the higher capacities make bulk storage more affordable long term.
Recommendations On Choosing the Right Hard Drive Type
We’ve covered a ton of technical nitty gritty details comparing shingled vs conventional hard drive technology – so what does it all mean? When should YOU buy one over the other? Here is my handy cheat sheet of recommendations based on common use case scenarios:
For gaming & video editing – CMR recommended
Faster sustained throughput delivers snappier load times jumping between video editing timelines or game levels. 4K footage also demands consistent high bandwidth.
As external backup drive – SMR makes sense
Occasional write performance matters less for backups and extreme SMR capacities max out affordability of cold storage.
As desktop internal drive – match to OS & programs
If running operating system and active programs aim for 7200 RPM CMR model. For pure bulk data then 5400 RPM SMR saves dollars.
For NAS enclosures – stick with CMR rated for NAS
Purpose built CMR drives handle vibration better thanks to rotational sensors and workload balancing suited to RAID.
When building datacenters – underlying hardware matters
At scale SMR can work reliably on server architectures explicitly supporting cache acceleration, robust RAM and Lawrence Livermore Labs developed drive formatting standard called Dynamic Drive Segment Interleaving enabling out of order writes.
The Future Remains Solid State
While this technology throwdown comparison focuses on CMR vs SMR hard drives using spinning magnetic platters to store bits, solid state drives offer a compelling heir apparent lacking most mechanical downsides. AES-256 hardware encryption further secures precious data against risks from degradation or device loss. And bandwidth measured in gigabytes per second instead of megabytes rapidly accelerates workflows.
The decision point for many data hoarders comes down to cost per terabyte where HDDs still maintain a healthy advantage despite rising densities on thumbstick sized SSDs. Industry experts expect near pricing parity within the next 5 years for bulk storage opening the floodgates away from mechanical dependence. Until then combining CMR drives for active working data and SMR high capacity storage for archived material makes perfect sense.
I hope this guide gives you ample technical background to make smart investments matching the right storage technology to your needs as the mass migration to solid state continues slowly but surely! Please drop me a note with any other questions. Talk soon!
