While seemingly mundane, choosing the correct hard drives for your NAS may result in a large difference in your experience, both with performance and reliability. You would think sorting by lowest price and going with the most cost-effective option work, as this was my initial thought. However, there is far more nuance to the final choice.
The most important consideration for a NAS drive will invariably be it’s reliability. This use case requires 24/7 uptime spanning as many years as the hard drive will allow. This immediately rules out any consumer-grade HDDs as most are rated for a 2-3 year duty cycle, failing far before their enterprise-grade counterparts. Even consumer drives advertised specifically towards NAS applications have been found to be less reliable (and at an equivalent price). Enterprise-grade drives are designed to live in racks for years at a time and are inherently rated for much higher & longer cycles before going out of spec compared to their consumer counterparts. Many of these drives can include additional features as well such as more robust power management, or acoustic control.
The second consideration will be performance. There are two types of drives available in this market: SMR (Shingled Magnetic Recording) and CMR (Conventional Magnetic Recording). The list of differences between the two is long and varied & suffice it to say that CMR is vastly superior both in terms of performance and reliability. SMR drives can be found at a discount compared to their CMR counterparts but would not be an appropriate choice for long-term deployment. Many times you will need to ensure that the specific model number of your drive is CMR, as both technologies have been found to be packaged under the same name and the same price by certain manufacturers.
So what was my choice? After navigating the surprisingly nuanced waters of storage options my ultimate choice for NAS storage was the Ultrastar HE8. At the time, refurbished options were a fraction of MSRP for consumer-grade 8TB drives and came with a 5-year warranty. Combine this with low power consumption (helium-filled), high relative performance and excellent reliability according to backBlaze statistics and they seemed the natural choice. Refurbished drives can be risky as the quality of the drive is a lottery, however with a RAID setup and warranty the risks can be largely mitigated.
Two and a half years into deployment and all 3 drives are still working as expected. One drive came unhealthy and would frequently kick the RAID 1 array offline due to long seek times but with the use of tools to scan the drive and remap bad sectors to new ‘spare’ sectors, this drive has returned to a reliable state. Generally this remapping will occur automatically, however with a group of ~2k sectors needing remapping it is more convenient to force a full scan, given that the drive would kick offline each time one is encountered. This drive will likely be the first to go as the S.M.A.R.T data continues to show an increasing number of pending sectors (read/write issues with the sector at least once) but appears to be in a holding pattern for the time being with additional spare sectors available for remapping if needed. However, the other two after ~5 years in a data center are holding strong 2.5 years later.
My choice for NAS drive applications would be a quality enterprise-grade SATA drive. Backblaze releases yearly drive reliability reports that can be used to make this decision without too much hassle. These choices will change regularly as newer drive technologies are rotated through data centers and come into general market availability. If some risk can be tolerated, refurbished drives may be a great option to save a few dollars. However, you will need to be prepared to deal with RMAs and be willing to check the S.M.A.R.T data for any potential issues.