How and Why are NAS Hard Drives Different from Desktop Hard Drives

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If you’ve ever wondered if you can use standard internal hard drives in your NAS server or why you may need to buy specially designed NAS hard drives for NAS servers then this article is for you. In this article, we will discuss why it is good practice to buy hard drives that are specifically built for NAS servers, advantages of NAS hard drives, and we will also compare NAS hard drives with standard desktop hard drives side by side with performance and hardware stats. And lastly, we will explore whether terabyte for terabyte, NAS hard drives are more expensive than standard internal hard drives used in desktop computers.

This article is part of a 4 part series about NAS or Network Attached Storage server. This series aims to answer questions like what is NAS, how can NAS solve your home storage needs, key features to think about before buying a NAS server, why are NAS hard drives different and what role does RAID play in your NAS server. Since the world of NAS is so vast, we have decided to split our articles into 4 key areas:

What is NAS, Benefits of Using NAS server and alternatives to NAS for home use
How to choose a NAS server and key features to consider before buying a NAS

How and why are NAS hard drives different from Desktop hard drives (you are here!)
What is RAID and how to make the most of RAID levels in your NAS server (coming soon)

Internal hard drives for desktop computers are only required to read and write data for several hours a day. In contrast, NAS hard drives will have to endure reading and writing of data for weeks and months on end as a NAS server is designed for an “always on” style operation.

As a result, NAS hard drives will have to have the following key properties that normal desktop hard drives don’t necessarily need to have:

  • Ability to operate under higher vibration in a NAS enclosure
  • Ability to function at a higher temperature in a NAS enclosure
  • HDD hardware suitable for continuous operation for weeks and months
  • RAID friendly firmware

NAS hard drives have higher temperature and vibration tolerance

NAS hard drives are more resilient to vibration and heat as they will be housed in a case with lots of other internal hard drives that run all at the same time. Whereas for a typical desktop computer unit, you’d expect to have only 1 or 2 internal hard drives. Therefore, noise or vibration may not be a key concern. 

However, in a NAS, you’d typically be looking at 2, 4, 6 or even more hard drives all compactly fitted inside a small casing unit. On top of that, if you go for a high spindle spin rate (RPM) hard drive for faster data transfer speed, then this will cause even more vibration and heat. As a result, in a NAS server, you will need a hard drive that is resilient to both vibration and higher temperature than desktop hard drives. 

Most NAS hard drive manufactures will have some type of additional vibration resistant features built into their NAS hard drives. For example, Seagate have Rotational Vibration sensors in all their Ironwolf NAS hard drives, and also in their Exos enterprise hard drives.

Western Digital also claim that their WD RED NAS hard drives come with advanced vibration protection.

NAS hard drives are suited for continuous operation

Most desktop internal hard drives are designed to operate only several hours per day. During this time, they will read and write a limited amount of data. A hard drive’s duration of operation is measured in Mean Time Between Failure or MBTF in short. And its data transfer capability is measured as workload rate, calculated as Terabytes of data transferred per year or TB/yr. 

An entry level purpose built NAS hard drive will come with 180 TB/yr workload capacity rating. This is in contrast with most desktop hard drives that come with 50 – 60 TB/yr rating at best. Higher end NAS hard drives like Seagate Ironwolf Pro come with 300TB/yr work load capacity. And if you move to Seagate Exos Enterprise, then this changes to 550 TB/year which is almost over 10 times higher workload capacity than a desktop hard drive.

Similarly, MBTF or mean time between failure, is a statistical term that calculates the relative reliability of a family of products and is measured in hours. Most NAS hard drives come with a minimum of 1 million hours MBTF rating. However, this does not mean that your hard drive will last for 114 years! [(1,000,000 hours / 24 hours) / 365 days in a year = 114.15 years]. If a hard drive lasts for 114 years, all hard drive manufacturers will go out of business. 

One can make a valid case arguing that MBTF isn’t necessarily an accurate way of measuring hard drive longevity in hours as this is based on a large number of hard drives running in a controlled environment in a test site. The data is then extrapolated using various statistical models to arrive at the MBTF rate. Therefore, manufactures like Seagate have stopped using MBTF rating and have started their own standards i.e. AFR by Seagate. Seagate AFR will show the count of probable percent of failures per year based on their total number of installed units of similar type vs MBTF which counted average number of service hours between failures in a test environment.

Anyhow, MBTF rating is still shown in Seagate and Western Digital NAS hard drive spec sheets. However, both Seagate and WD don’t show MBTF rating for their desktop hard drives.

Most desktop hard drives have an MBTF rating of 300,000 and up compared to Seagate Ironwolf starting at 1 million hours, Ironwolf Pro at 1.2 million hours and Seagate Exos with 2.5million hours.

So as you can see from the above, NAS hard drives tend to have much higher continuous operational capability both from workload and operating hours point of view.

Custom firmware suited for NAS server

From a software perspective, NAS drives also come with a slightly different firmware that is geared towards operation in a RAID environment. In standard internal hard drives, when a sector of data becomes corrupted, the internal hard drive’s firmware will repeatedly try and recover the data resulting in timeouts. As the desktop hard drives are not designed for a RAID environment, they will prevent the RAID controller from kicking in to fix the error. This may result in the hard drive disconnecting from the RAID system.

However, a NAS hard drive’s firmware will make sure that it does not keep trying to recover the data, but refer the issue as an error to the NAS server’s RAID controller. RAID controller will then be able to recover the data from another hard drive i.e. if the data was stored with a RAID level 1 or above.

Are NAS hard drives more expensive than desktop hard drives?

It is often assumed that NAS hard drives are significantly more expensive than standard desktop hard drives. However, the difference in cost per Terabyte is not as big as one would imagine.

We went on a quick shopping spree on some online retailer websites and collated prices for Western Digital and Seagate hard drives. For WD, we compared WD Blue (desktop HDD) with WD RED, WD RED Plus and WD RED Pro. And for Seagate, we compared Barracuda Compute with Ironwolf, Ironwolf Pro and Exos Enterprise. 

We checked Ebuyer.com, Scan.co.uk and Western Digital’s own website and recorded the cheapest price across those 3 sites for each of the hard drives.

These prices were obtained in Feb 2021. When a HDD was available on all 3 sites, we took the cheapest price available. Some retailers were running promotions/discounts on certain hard drives so the prices may not be 100% comparable. However, the above prices are exactly what a consumer would have paid on the day we checked the prices on the 3 websites.

For comparison purposes only, if we look at the cost of 3.5” 4TB internal hard drives on offer from Seagate, then you will notice that the cost per TB for Barracuda Compute is £19.25. 

For an Ironwolf version of the same 4TB hdd, the cost per TB comes in at £24.75. This is 28.59% more expensive than the desktop Barracuda 4TB. Ironwolf Pro comes in at £29.12/TB, which is 51% more expensive than the desktop version.

However, if you look at the table for Western Digital above, you will notice that WD’s entry level NAS hard drive, WD Red’s cost per TB comes in at £22.75/TB for a 4TB hard drive. When compared to WD Blue desktop hard drives of the same capacity, this is only 18.2% higher in cost. Nevertheless, there is a minor catch here. WD Red hard drives (not WD Red Plus or Pro) use Shingled Magnetic Recording technology or SMR in short. SMR is believed to be more suitable for backup or archive data. 

Therefore, if you move one level up to WD Red Plus which uses CMR (Conventional Magnetic Recording) technology, then cost per TB for a 4TB WD Red Plus hard drive comes in at £24.50 compared to £19.25 for WD Blue. This is 27.28% higher and very much in line with the price difference between Seagate Barracuda and Ironwolf (28.59%) 4TB drives.

So we can conclude that based on the price checks above, NAS hard drives are indeed slightly more expensive than desktop hard drives. However, as discussed in the sections above, this 28% or so extra cost is definitely worth investing considering factors such as:

  • Higher workload rate 50TB vs 180TB (starting) which is 3.5 times more
  • Higher MBTF (how long your drive can last) which is also 3 times or higher
  • Longer warranty periods
  • More compatible firmware for RAID in NAS
  • Better vibration control and thermal efficiency

We hope that this article has been able to give you a rough idea on how NAS hard drives are different from standard desktop hard drives. We also hope that this article will help you decide whether NAS drives are more expensive than desktop hard drives. Please feel free to reach out to us or comment below if you have any suggestions or would like to add anything we may have missed. Thanks and speak soon!

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