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Best M.2 NVMe SSD for NAS caching



More NAS enclosures are coming with M.2 SSD slots for speedy NVMe flash drives. The aim of these slots is to allow for improved overall system performance by allowing the OS to store frequently accessed data, acting much like secondary RAM. Here’s why you may want to use an SSD for caching and what are your best M.2 NVMe SSD for NAS options.

What is the best M.2 NVMe SSD for NAS caching?

The best M.2 NVMe SSD for NAS caching is one that has enough capacity to actually make a difference to overall system performance. It also requires a good endurance rating for better reliability and a longer lifespan, and you should look for a drive with a specific NAND technology, if possible. You don’t have to choose the best NAS to get M.2 slots either.

Overall, I’d recommend the Western Digital Red SN700, which has a good 1 drive write per day (DWPD) endurance rating, is available in sizes up to 4TB, and is SLC (arguably the better technology choice for NAS caching). A close second place goes to the Seagate IronWolf 525, which has similar specifications to the SN700 but utilizes TLC.

If you’re all about endurance and seek the best cache drives around, look no further than Intel’s Optane range. The Intel Optane DC P4801X is excellent with a class-leading DWPD rating. This is the drive to get if you have a performance issue on your NAS and don’t mind spending a small fortune on an SSD.

Read-only NAS caching

The easiest way to configure an NVMe SSD for NAS caching is to use it for read-only caching. The OS will move across the most frequently used files to this SSD, allowing services to call upon this data without touching the main drive array. This process prevents any modifications from being made to data on the cache.

A read-only cache should primarily be used by those who are accessing large amounts of stored data on the NAS that isn’t modified often. But it does result in more efficient SSD caching due to the read-only limitation allowing the drive and its controller to work out precisely what should be stored for better access.

Write NAS caching

Writing to an SSD cache on NAS is a whole different story altogether. There are various types of this form of cache with the first being write-through caching. This involves simultaneous writing to both the drive array and SSD cache. This allows the main array to keep the data should an issue cause a system failure or loss of power.

It’s safer but lowers the access speed for data. An alternative way for writing to cache is what is known as write-back caching. This process only writes data to the SSD cache before copying it across to the main drive array. This offers lower latency for accessing data but does mean you may encounter data loss through a system failure.

What SSD capacity do you need for NAS caching?

Using an NVMe SSD for NAS caching is a totally different kettle of fish compared to buying the outright best SSD for NAS with your storage pool in mind. The latter is primarily used for expanding the amount of capacity you have for storing data in the drive array.

SSD caching is for improving the performance of your NAS when dealing with lots of data (and simultaneous connections). For the capacity of NAS SSD caching drives, you won’t really require anything more than 250GB, unless you’re dealing with large files in a frequent fashion.

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My top NAS caching SSD recommendations

Western Digital Red SN700

Best overall SSD for NAS caching

Western Digital Red SN700
Western Digital Red SN700. (Source: WD)

Western Digital’s Red SN700 series of M.2 SSDs are brilliant for storage and caching. They have decent endurance ratings, come with a five-year limited warranty, and are in capacities that top out at 4TB.

Capacity250 GB – 4 TB
Endurance~1 DWPD
Speed~3,430 MB/s
Warranty5 years
  • Better value
  • Up to 4TB
  • SLC
  • Still expensive
  • Not the fastest
DriveSpeedEnduranceWarrantyPrice$ per GB
Western Digital Red SN700 250 GB3,100 MB/s1 DWPD5 years$64$0.26
Western Digital Red SN700 500 GB3,430 MB/s1 DWPD5 years$53$0.11
Western Digital Red SN700 1 TB3,430 MB/s1 DWPD5 years$85$0.09
Western Digital Red SN700 2 TB3,400 MB/s0.7 DWPD5 years$152$0.08
Western Digital Red SN700 4 TB3,400 MB/s0.7 DWPD5 years$280$0.07

Whether you’re looking to expand your NAS capacity with some speedy flash technology or want one of the better drives to use for SSD caching, the Western Digital Red SN700 is one you should strongly consider. It’s well-priced, has good endurance ratings across the range, and is available in capacities up to 4TB.

Speaking of endurance, which is incredibly important for reliability (especially so if writing through cache), the most affordable 250GB Red SN700 SSD has a drive write per day (DWPD) rating of 1, meaning you can effectively write 250GB to this SSD per day for the five years of its warranty lifespan.

A bonus to this SSD is the speed, allowing data transfers of up to 3,430MB/s, which is incredibly fast compared to SATA HDDs and SSDs. SLC NAND technology is also used, which is great for enhancing reliability through heavy caching workloads. It’s an all-around rock-solid SSD.

Seagate IronWolf 525

Runner-up best SSD for caching

Seagate IronWolf 525
Seagate IronWolf 525. (Source: Seagate)

Seagate is a fierce competitor of Western Digital. It produces some great storage solutions for NAS enclosures, including the IronWolf 525. These drives are designed for cache use and have good endurance with sizes that top out at 2TB.

Capacity500 GB – 2 TB
Endurance0.8 DWPD
Speed~5,000 MB/s
Warranty5 years
  • Up to 5,000MB/s
  • Great performance
  • Capacities up to 2TB
  • Expensive
DriveSpeedEnduranceWarrantyPrice$ per GB
Seagate IronWolf 525 500 GB5,000 MB/s0.8 DWPD5 years$100$0.20
Seagate IronWolf 525 1 TB5,000 MB/s0.8 DWPD5 years$204$0.20
Seagate IronWolf 525 2 TB5,000 MB/s0.8 DWPD5 years$310$0.16

The Seagate IronWolf 525 series is essentially a direct competitor to the Western Digital Red SN700. They’re both relatively similar, except Seagate makes use of TLC NAND technology and this is one of the primary reasons why these drives are ranked second place.

Endurance also takes a small hit because of this, though it’s still high enough for them to be used as caching drives. The choice of 500GB, 1TB, or 2TB is a little limiting and it would have been good to see a 250GB version since even 500GB of caching could be overkill for many enclosures.

A five-year limited warranty and a decent price for each capacity make the IronWolf 525 a good choice for anyone wanting a slightly better value SSD cache or flash-based data storage.

Intel Optane DC P4801X

Best endurance SSD for caching

Intel Optane DC-P4801X
Intel Optane DC-P4801X. (Source: Intel)

Intel’s Optane family of products is a premium storage solution. Optane memory is designed specifically to improve the performance of existing storage, namely hard drives. They have ridiculously good endurance and are capable of handling heavy workloads without issue.

Capacity100 GB
Endurance60 DWPD
Speed~2,200 MB/s
Warranty5 years
  • Best-in-class endurance
  • SLC
  • Limited capacities
  • Seriously expensive
DriveSpeedEnduranceWarrantyPrice$ per GB
Intel Optane DC P4801X 100GB2,200MB/s60 DWPD5 years$170$1.70

Ignore the $ per GB for the Intel Optane DC P4801X for a moment, would you? This Intel drive is serious business and it all starts with that Optane memory technology. Optane is essentially Intel’s answer to turning slower existing drives into something more special without requiring the purchase of replacement SSDs.

The company achieves this through the Optane technology itself, which was specifically designed for use as a cache. It’s NAND flash-based but comes with some qualities usually reserved for RAM, except it’s non-volatile. This results in an incredibly high endurance rating of 60 DWPD.

You wouldn’t really want to use Intel Optane SSDs such as this for actually storing data, unlike all the other SSDs in this collection. Intel Optane is the only drive here specifically designed for data caching, making it the best choice for those who don’t mind spending a fair amount for the luxury.

Samsung 970 EVO Plus

Best value SSD for caching

Samsung 970 EVO Plus
Samsung 970 EVO Plus. (Source: Samsung)

Samsung is a big brand in the memory game and its 970 EVO range of M.2 SSDs is brilliant for desktop and laptop computers. They can also technically be used in NAS for caching, saving you some money in the process compared to specifically designed modules.

Capacity250 GB – 2 TB
Endurance0.3 DWPD
Speed~3,500 MB/s
Warranty5 years
  • Excellent performance
  • Good value
  • Low endurance
DriveSpeedEnduranceWarrantyPrice$ per GB
Samsung 970 EVO Plus 250 GB3,500 MB/s0.3 DWPD5 years$30$0.12
Samsung 970 EVO Plus 500 GB3,500 MB/s0.3 DWPD5 years$38$0.08
Samsung 970 EVO Plus 1 TB3,500 MB/s0.3 DWPD5 years$70$0.07
Samsung 970 EVO Plus 2 TB3,500 MB/s0.3 DWPD5 years$97$0.04

I’m a huge fan of the Samsung 970 EVO Plus range for gaming desktop PC use. These drives are fantastic in terms of performance and value. You’ve got the same five-year limited warranty from Samsung as you do Western Digital with our top recommendation here, but there are a few small drawbacks with the EVO Plus.

Firstly, it utilizes TLC NAND technology, which isn’t the best for caching. If you’re working with big data and start hitting these drives hard, you could encounter an instance where it may hang and cause the NAS to shut down. For most people, however, no issues should arise (and you should be backing up your NAS data regularly, right?).

The available capacities are also limited, only going up to 2TB, though you really shouldn’t require more than 250GB for SSD caching, regardless. A great choice for SSD caching if you’re looking to save a little.

Western Digital Blue SN570

Best budget SSD for caching

Western Digital Blue SN570
Western Digital Blue SN570. (Source: WD)

Looking at the specifications of the Western Digital Blue SN750 range it’s clear to see these drives were designed for storing actual data, instead of being used as a cache. But you could absolutely use them to give your NAS a boost, just be sure to back up your data often.

Capacity250 GB – 2 TB
Endurance0.3 DWPD
Speed~3,500 MB/s
Warranty5 years
  • Affordable
  • Good range of capacities
  • Performance
  • Endurance
  • Reliability
DriveSpeedEnduranceWarrantyPrice$ per GB
Western Digital Blue SN570 250 GB3,300 MB/s0.3 DWPD5 years$22$0.09
Western Digital Blue SN570 500 GB3,500 MB/s0.3 DWPD5 years$40$0.08
Western Digital Blue SN570 1 TB3,500 MB/s0.3 DWPD5 years$45$0.05
Western Digital Blue SN570 2 TB3,500 MB/s0.3 DWPD5 years$93$0.05

If all you care about is price, look no further than the Western Digital Blue SN570 series of M.2 SSDs. These affordable drives are perfect for replacing mechanical hard drives in desktop and laptop computers, but they could also be used for storage and even some caching on NAS. Just don’t expect much from the drives in terms of endurance.

The 0.3 DWPD rating is awful compared to everything else in this collection. I would highly recommend you avoid using the Blue SN570 for writing cache. So long as you’ve backed up your data and plan to only use these drives for read-only, you should be fine.

The selection between 250GB and 2TB also isn’t the best, but it’s not terrible. There’s still a five-year limited warranty, at least.

Synology SNV3410

Best for Synology NAS

Synology SNV3410
Synology SNV3410. (Source: Synology)

Synology has its own branded M.2 NVMe SSDs available for not only its own NAS but also competitor enclosures. They’re reliable, fast, and relatively expensive.

Capacity400 – 800 GB
Endurance491 TBW
Speed~3,000 MB/s
Warranty5 years
  • Supported with Synology NAS
  • Excellent endurance
  • Great performance
  • Expensive
  • Limited capacities

Do you own a Synology NAS and would prefer to stick to first-party branded parts, the Synology SNV3410 range of M.2 NVMe drives is what you should be considering. Capacities range between 400 GB and 800 GB, which doesn’t provide much in terms of storage space, but these drives are excellent for caching.

With an endurance rating of 491 TBW and a top read speed of 3,000 MB/s, you’ll be storing and extracting data without delay, boosting the performance of your enclosure. They’re not cheap with the 400 GB model starting at $150, but these SSDs integrate well with Synology’s DSM operating system.

DriveSpeedEnduranceWarrantyPrice$ per GB
Synology SNV3410 400 GB3,000 MB/s491 TBW5 years$150$0.38
Synology SNV3410 800 GB3,000 MB/s491 TBW5 years$280$0.35


Not all flash-based storage drives are the same. NAND flash cells are usually categorized based on the number of bits that can be stored per cell. Watch out for the following terms when shopping around for an SSD:

  • Single-Level Cell (SLC): one bit per cell.
  • Multi-Level Cell (MLC): two bits per cell.
  • Triple-Level Cell (TLC): three bits per cell.
  • Quad-Level Cell (QLC): four bits per cell.

So, does it actually matter which technology is used for NAS SSD caching? Actually, yes it does. When looking for the best M.2 NVMe SSD for NAS data caching, it’s important to bear the NAND technology in mind.

SLC is the best technology for SSDs that will be used for NAS caching. This does mean you’re paying out more per GB and won’t be able to select high-capacity drives, but reliability and the protection of stored data is the most important factor here.

Another benefit of SLC is the lower impact of write amplification, which can quickly creep up and chomp through a drive’s DWPD endurance rating. It’s important to configure an SSD for caching correctly too regardless of which technology you pick.

Doing so will lessen the likelihood of losing data through a drive hanging and causing the system to crash. Anything stored on the cache drive that has yet to be written to the main drive array would be lost. This is mostly a reported issue for NVMe drives, as opposed to SATA.

What is DWPD and why is it important?

DWPD stands for drive writes per day. This is often used as a measurement of a drive’s endurance. The higher this number, the more writes the drive can perform on a daily basis, as rated by the manufacturer. For caching, especially which involves writing data, you’ll want to aim for as high a DWPD rating as possible.

Do you really need SSD caching?

Probably not. That’s an honest answer here. A lot of the marketing surrounding M.2 slots, including what you’ll see here in our own reviews, is just that — marketing. These slots cannot be used for adding additional flash storage for your pool and are restricted to just caching.

So what should one do before considering SSD caching on NAS? Try installing more RAM, if possible. Many enclosures, especially with Intel processors, support more RAM through the use of a spare RAM module slot. It’s even possible to go beyond the maximum officially stated capacity. Just be sure to do a little research beforehand.

SSD caching acts very much like slower RAM, so upgrading the amount of memory the NAS has to play with is a good place to start before making a purchase on an M.2 SSD. I’ve written guides on most NAS enclosures that support the upgrading of RAM, so be sure to do a local search on NAS Master.

Richard Pinnock-Edmonds Avatar

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