There are many reasons you should use a hard drive for archival storage and data backups. If you compare hard drives with Solid State Drives, in terms of cost, storage density, and reliability, hard drives are generally considered better in most areas. They surely have some drawbacks but still, I would like to discuss their effectiveness when it comes to raw data storage like backups, and databases. etc.
I am not saying SSDs aren’t reliable but the basic storage functionality is different and SSDs have much more fragile or unstable methods of storing data as compared to hard drives. Hard drives, with the help of magnetic material as their storage medium, tend to hold the data in a much better manner. SSDs, on the other hand, hold to data in the form of electric charge which eventually leaks out if we keep SSDs idle for long periods. Modern SSDs especially the 3D NAND with charge-trap flash storage have more resilience and charge-holding capabilities, but still hard drives are considered much more reliable for long-term data storage.
Understanding the AFR
If you check studies that compare, most of them conclude that the SSDs are more reliable than the hard drive. However, most of these studies are done in big data centers and on enterprise SSDs (mostly SLC). Definitely, an SLC would beat any hard drive in terms of both performance and data retention. But, this isn’t the case with consumer drives.
Most studies give the AFR (Annual Failure Rate) as a very important criterion for deciding an SSDs reliability. AFR represents the percentage of devices that are expected to fail in one year out of the total number of devices. If an SSD has an AFR of 1%, this means that out of 1,000 SSDs, approximately 10 are expected to fail in a year.
The very popular BackBlazes studies on both HDD and SSD conclude that SSDs are more reliable with the average AFR (Annual Failure Rate) of SSDs is 1% throughout the 4 years of this study. The AFR of Hard drives in these studies is generally between 1 to 2%. In previous years, the hard drives were coming up with AFR numbers like 5.23% and even 6.93%. Now, in the year 2024, the AFR of HDDs and SSDs is closer. However, this study is happening on some drives and their specific models. Doing this type of study is hard because of hundreds of different drives and their different models from many brands.
Benefits of Hard Drive for Raw Data Storage
Hard Drives are good in terms of cost-to-store density ratio as compared to solid-state drives. But, there are some specific benefits that you get only with the hard drives. Let’s discuss them.
1. Data Longevity
For archival storage, data longevity is perhaps the most important thing to consider. Typically, Hard Drives can last 5 to 10 years when used properly and stored in optimal conditions. Cool and dry environments are beneficial to long-term data storage. Compared to the SSDs, Hard Drives can hold the data for longer when stored without power. This is because of the magnetic storage medium which is less susceptible to degradation without power.
Hard Drives mostly fail due to mechanical failures which can easily be avoided with proper care. Because there is no charge, there is no charge leakage in hard drives. Also, the write operations are not very destructive for the memory blocks in a hard drive as compared to the SSDs. This problem is even worse when we use the QLC drives for raw data storage for the long term.
2. Read/Write Cycles
SSDs come with a limited number of Program/Erase cycles which when surpassed, makes the SSDs less reliable for data storage. Hard Drives can also degrade with prolonged use but the effects aren’t very intense. So, you can trust more on a used hard drive for long-term storage than a used SSD.
3. Lower Risk of Data Corruption
The magnetic storage nature of the hard drives makes them more reliable because of their stability. Bit rot (because of high temperature, humidity, and magnetic fields) can easily be avoided with proper management of your drive. The ECCs work well while reading the data because of have only two magnetic fields.
4. Ease of Data recovery
As long as the magnetic platter of your hard drive is in good condition, the data from a bad drive can easily be recovered. Because of a matured storage technology, hard drives have much better data recovery services available.
5. High Capacity at Low Price
Hard Drives cost approximately $15-$25 per TB for consumer-grade drives (high-capacity models can go as low as $15/TB). A normal consumer SSD can cost you between $70 to $100. Overall, SSDs come at nearly 300-500% higher cost per TB compared to the Hard Drives. This makes the hard drives more practical for long-term, large-scale archival storage.
Things to Remember for using hard drives for cold storage
The most important thing is to store your drive in an optimal condition. Using your hard drive in a cool and dry environment is recommended. Also, keeping it away from dust and vibration is a good thing. Spin up your archival drives every few years or months to check for mechanical functionality and ensure the data is still accessible. Because hard drives are cheaper, it is easy to set up RAID (in case of hot storage) or use multiple copies of your data in different drives (in case of cold storage).