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What is SSD cache on NAS and why should you use it?

Read all about SSD caching, why it’s important and how to use it.

SSD cache inside a NAS enclosure can considerably improve the read and write speeds of installed mechanical hard drives in select workloads. While this won’t affect sequential tasks like streaming media, using cache can have a huge impact when running virtual machines and other intensive computing.

Does my NAS support SSD cache?

Most (if not all) NAS should have some form of SSD support. All you need to do is buy and install M.2 or SATA SSDs and configure them in the OS. Once everything is up and running, the NAS will be able to utilize these drives to boost read and write performance.

While SATA SSDs can be used, I’d always recommend using M.2 slots if they’re available. This helps keep all the drive bays free for actual storage.

How does SSD cache help NAS?

SSD caching is available on select NAS enclosures, usually more expensive models with numerous bays. SSD caching is viewed as a middle ground between hard drives and solid-state drives for storage. Going all-out with SSDs for storing data can get really expensive. Using the best NAS drives with SSD cache helps you save a little.

SSD cache allows you to use hard drives and take advantage of some of the benefits of solid storage. Think of computer RAM and you’re getting on the correct track. Hard drives are great for sequential data transfer, where it’s all stored together, but when you need data from different parts of the drive, you’ll encounter some latency.

This is where SSD caching comes into play. Frequently-accessed data can be stored on the SSDs that can be used by the OS instead of going directly to the hard drive. There are two types of caching on NAS, read-only and read-write.

The former only sees the OS read frequently-accessed data on the cache drive. Read-write cache involves writing data to the SSD.

How much SSD cache do you need?

How much SSD cache you need depends on the number of hard drives installed as well as volume capacities. I’d recommend at least 500GB for caching SSDs. You’d ideally want 1TB if you have 70TB or more worth of data stored on the NAS. You can use either M.2 or SATA SSDs.

I recommend going with an SSD that has solid endurance. Using the SSD as a cache involves a lot of writing to the drive, which is why I use Seagate IronWolf 525 SSDs, one of the best NAS SSDs.

SSD caching doesn’t affect Plex

If the primary use of your NAS enclosure is for Plex and media playback, SSD caching won’t really make a difference. A Plex server reads metadata and other information, but when it comes to streaming the video files, this relies on sequential reads.

Synology SAT5200

Synology SAT5200

Synology’s SAT5200 range of solid-state drives is brilliant for server use. If you want to boost your existing NAS transfer speeds with some cache or replace the HDDs with flash storage, look no further than these puppies.

Seagate IronWolf 525

Seagate IronWolf 525

M.2 drives are usually restricted to acting as SSD cache and as such aren’t able to expand the capacity of your NAS. This does allow you to pick up an M.2 drive like the Seagate IronWolf 525 and not waste any of your existing drive bays.

By Richard Edmonds

I've been covering the tech industry for more than a decade and have tinkered with NAS for just as long. Follow my ramblings and more right here on NAS Master!

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