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NAS Hard Drives Buying Guide

There are three types of hard drives suitable for a NAS server: 2.5 'HDDs, 3.5' HDDs and SSDs. In this guide, we explain everything you need to know before you start buying SSDs for your Network Attached Storage.

You can also check our NAS Hard Drives Buying Guide for more related information.


SSD versus HDD

To highlight the differences between SSDs and HDDs, let's compare them to each other and we will find that they don't have much in common.

Like a record player, an HDD hard drive uses a tonearm to write and read information on a magnetic platter that spins at high speed.

SSD (Solid State Drive) storage does not contain any moving parts. It relies entirely on flash memory in the form of microchips on which data is read at the same time. This operation has the consequence of drastically accelerating the speed of reading information.

In addition, the absence of moving parts decreases the risk of mechanical failure of the drive while making it less sensitive to shock and vibration, leading to a more durable and reliable solution than HDD. The lifespan of an SSD is counted in number of terabytes written (TBW). TBW is the maximum amount of data that can be processed by a SSD drive, and it is indicated by the manufacturer. After this amount of data is done, the SSD drive is to be considered unreliable. However, studies show that SSDs last between 2.5 times and 60 times longer than what is reported by the manufacturer. On paper, the SSD has a shorter lifespan than HDD but in reality, that's not confirmed.

Another major advantage in the SSD drives is the absence of noise, because of not having any moving parts . You will therefore only hear the noise of the fan on your NAS.

The power consumption of an SSD is reduced by about 60% compared to an HDD. The electrical cost of a 2-bay NAS server which is used on a regular basis will not exceed $20 / year, which may not justify the investment in SSDs with the sole objective of reducing power consumption costs.

Finally, SSDs are smaller than 3.5 'HDDs. Adopting a full SSD solution or combined with 2.5 'HDD makes it possible to reduce the size of the boxes . Synology also offers consumer boxes exclusively reserved for the use of 2.5 'drives such as the DS419Slim and DS620Slim. The boxes then become more and more compact. The DS419Slim measures for example 120 mm x 105 mm x 142 mm while a DS418 measures 166 mm x 199 mm x 223 mm.

The evolution of the SSD hard drive market

The SSD is the next generation of hard drive and will gradually replace the HDD which will eventually only be kept for storing large databases in Datacenters for example. SSD only has advantages over HDD but it is the cost of SSD storage that has slowed its expansion in the market.

But the cost of flash memory has fallen over the years to such an extent that today SSDs are largely affordable, even though the cost of gigabit remains higher than that of HDD. Now even on entry-level PCs we are starting to see the appearance of SSDs, a sign that this type of storage is becoming more popular.

So how worthwhile is it to invest in SSDs for a NAS server? Read on to get an answer!

Why use SSDs on a NAS server?

1- Improve caching

What is mostly sought after by NAS users who invest in SSD is the caching acceleration.

Coupling SSDs with HDD hard drives,  is the most economical solution, since it will only require the installation of the SSD partially while allowing to keep a large storage capacity with HDD.

In this case, most of data transfers in progress will go through the SSD, which will double or even quadruple the speed of managing common tasks. However, if you want to keep a RAID configuration of your data, you must have a NAS with a minimum of 3 bays.

Each manufacturer offers different options and ways to manage cache, but be aware that not all NAS models are compatible. With Synology for example, only high-end NAS are compatible such as DS718 + , DS918 + or even DS620Slim.

On the other side, with QNAP, the compatible models are much more extensive.

Pay attention to the memory available on the NAS also which determines the maximum cache size on the SSD. For 515GB of cache you will need 1GB of available RAM, while 8GB of RAM will allow you to manage cache sizes of up to 2TB.

Finally, it is recommended to use an SSD with a size corresponding to 10% of the total capacity of the hard disks after RAID. If you want to go further in the optimisation, the ideal is even to use two SSDs, one for the read cache and the other for the write cache.

2- Improve performance

The main advantage of SSDs is the much faster data access speed than HDDs. With a transfer rate of more than 500 M /s, you will still be limited by the capacity of your internet connection which is still often capped at 100Mb/s for individuals. But the deployment of NBN on a large scale and the gradual arrival of Wifi 6 is helping in achieving higher speeds.

If your internet connection -theoritically- works on 10 Gb/s, you can fully benefit from the performance boost provided by SSDs. In this case, you will need to install a full SSD configuration, which can be quite expensive. But you can also compartmentalise your storage volumes to reduce costs and rationalise utilisation rate versus performance. This is called a storage pool.

For example, you keep personal files on HDDs and other files you share with other users on SSDs. And if you are into content creation, it can also be interesting to work on files stored on SSD while archiving your work on HDD.

3- Reducing noise

Some users have technical constraints related to installing their NAS at home. If you want to install a NAS in a bedroom, you will need to be a heavy sleeper so you won't be disturbed at night. Especially if you have scheduled automatic backups during this time. SSDs will remove any vibration noise from hard disks, leaving you with the fan noise only, which is reasonable.

The type of SSD connection


SATA SSDs are most commonly used on NAS servers. The SATA connector is also the one used for HDDs, which makes it easy to exchange with each other without changing the connector.

You just need to add an adapter in the bay to integrate an SSD in your NAS, just like in a PC.

The theoretical transfer speed of SATA SSDs tops out at 600 Mb/s . This is much more than the 120 Mb/s of an HDD.

2- M.2 SSD

The M.2 format is the successor to the SATA format. M.2 connectors are still not very popular with NAS for the general public. M.2 SSDs have the advantage of being smaller than SATA, thanks to the absence of a case. They can then be positioned in locations provided for this purpose and leave the bays free for larger HDDs. There are M.2 SSDs that offer the same transfer speed characteristics as SATA.

NVMe SSD (stands for Non-Volatile Memory Express) is the latest generation of SS . The Synology DS918+ is equipped with an M.2 connector to accommodate them but the cost of this type of SSD is higher. The theoretical maximum speed is much higher than SATA with a maximum of 3 Gb/s.

If your NAS does not have an M.2 connector, it is possible to add a PCIe expansion card with M.2 connectors. Always check the compatibility on the manufacturer's website before installing a third-party brand card.

Top SSDs for NAS storage

1- Seagate Ironwolf

Without going too far into technical details, the Seagate Ironwolf offers three advantages compared to a classic SSD from brands such as Samsung or Sandisk.

  • The DuraWrite technology which allows data to be compressed and thus to reduce the flash memory used and to increase the life of the SSD.
  • A data recovery service for 2 years. Seagate is the only brand to offer this type of service by default on its hard drives. There are obviously terms and conditions and any data recovery has its limits, but this service alone justifies choosing Seagate.
  • Seagate provides a 5 year warranty on its IronWolf drives.

Shop Seagate Ironwolf NAS SSD Drives »

WD Red SA500

WD was quick to follow suit by announcing the arrival of its own line of SSDs for NAS.

Western Digital promises 560MB/s read speed and 530MB/s write. WD also offers the following specificities on the SA500 range:

  • 5 year warranty, like Seagate
  • A set optimized caching for appropriate use NAS

The lack of data recovery service and lower endurance than Seagate SSDs allow WD to offer more competitive prices. If you are choosing between both, start with checking your endurance requirements, calculated in number of Terabytes written. Bear in mind that the 5-year warranty will not apply if you exceed the TBW communicated by the brand. WD also offers M.2 SSDs which are not NVMe and they display the same specifications as SATA.

Shop Western Digital NAS SSD Drives »

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