Everyone on Reddit and YouTube portrayed SSD caching as the magic pill for every performance woe I was facing on my NAS. After a point, I started to half-expect the NAS to fly as soon as I added SSD caching. It seemed like this hidden performance switch — something that would instantly make file transfers faster, Plex streams smoother, and the whole interface feel like it was gliding on butter. And I had little reason not to believe it.

So, one fine weekend afternoon, I slotted in a pair of NVMe drives into my NAS, set them up for read and write caching, and sat back, ready to be blown away.

First came a lot of convincing that it actually worked, and that the NAS was indeed faster. But the reality had to set in sooner or later — and it did. Cache isn’t something you see or hear working, like you do with hard drives, but it does have a visible impact on your system. The effect it had on mine was much subtler than I had hoped for (or maybe I just set my expectations too high). It felt like the same system it was before installing those M.2 drives.

The caching reality

Managing your expectations

The idea behind caching sounds perfect — your NAS uses SSDs as a middle layer between slower hard drives and memory. It stores frequently accessed data (take note of this phrase, because I’ll bring it up again later) on the SSDs, so the next time you open your files, they load faster. It simply helps speed up accessing the stuff that you open frequently.

The problem is that home NAS workloads are rarely predictable or repetitive enough for caching to make a real difference. I use my NAS for things like streaming media, backing up my laptops, storing photos and videos, and handling some surveillance footage. Once my work files are moved to the NAS, I access them probably once in a fortnight when a project demands referencing old stuff — if at all. That’s a far cry from the frequently accessed data that caching is made and intended for.

In my case, transfers over the network were still limited by Gigabit Ethernet speeds — something no amount of caching could fix for good or even improve by a significant margin. Sure, there were some improvements: Synology Photos indexing became a tad smoother, and searching through Drive was a split second faster. But these changes certainly weren’t game-changing.

My system needed something else

And it wasn’t caching

I decided to test out all combinations to figure out what exactly my system needed to speed up. The first obvious step was to turn off SSD caching (and use the drives elsewhere) — and as you’d expect, nothing broke. Transfers didn’t slow down, and media streaming didn’t experience any buffering — clear signs that SSD caching was overkill, something my workload didn’t actually need.

The next step was to check for all the other actual bottlenecks — no, drives weren’t one of them — and fix them one by one.

A major relief came from something you just can’t run your NAS without: RAM. Mine came with 4GB of RAM, which I doubled to 8GB and saw instant results. DSM no longer needed to swap memory during big tasks, and my Docker containers ran much smoother. As for cache, with extra memory to spare, my system was able to handle the amount of caching I needed in memory itself. So before you go shelling out cash on NVMe drives, consider a RAM upgrade as the first step.

The next upgrade came in the form of networking. Since my NAS is an older model, it doesn’t support LAN port upgrades like many of the newer models do. While I could’ve benefited from a 2.5GbE port — especially when my family wants to stream 4K movies while I’m working — I had to find an alternative. It came in the form of link aggregation. I used the second LAN port on my NAS with the router (which also supports link aggregation) to double the available bandwidth for everyone on the network. This upgrade felt as if my NAS had learned to multitask.

Even with SSD caching, the network chokepoint would keep everything slow by limiting what flows through it. I opened that up with a simple trick, and things feel faster when everyone is using the NAS, even without SSD caching.

Living without SSD caching

But it’s not for everyone

SSD caching has its own upsides. It helps most with small, random reads and writes for things like virtual machines, hosting databases, mail servers, CRM systems, development environments, and more. But that’s not what I do on my home NAS, so SSD caching wasn’t the fix I was looking for.

RAM upgrades and link aggregation together have had a much more noticeable impact on my day-to-day operations than SSD caching did. Pair that with other minor optimizations, like timing sync and backup tasks for off-peak hours, and my system is now breathing much more comfortably.

While caching with NVMe drives may not have been a successful experiment on my end, it did improve my understanding of what really matters in setups like mine, and how I should manage expectations going forward. Because with so many moving parts, one fix just cannot work for everyone.