Roon and NAS SSD cache

Using a dedicated NUC for Roon and a Synology DS918+ NAS as the storage for all music seemed like the perfect solution. After a while something started to annoy me.

The four spinning hard drives in the DS918+ fell asleep after twenty minutes. So if I had not played any music for twenty minutes they would have to be spin up again, before I could hear any music. This process takes probably less than a minute, but when encountered often enough it started to feel like an eternity.

I had already expanded the DS918+ with a 4GB SO-DIMM and even though the extra memory is allegedly being used for cache also, I did not notice any improvements. My thoughts turned to the M.2 slots at the bottom of the NAS. Also, memory uses was quite low.

In articles and posts I read about the vulnerability of SSD caches, but wondered how serious of an issue this would be. Especially considering my use case. I would use a read only cache that would not have to deal with a lot of constant and intensive reads and writes . The idea being that it would only be filled with albums I regularly listen to.

So I ordered a Synology SNV3400-400G, which is a 400GB M.2 NVME drive. The install was a piece of cake. No screws needed. Just pop out one of the covers on the bottom of the NAS, install it, return the cover and start up your NAS. After that I only had to assign the SDD to cache duties.

At first, of course, the cache was empty, so when I played some music after the drives had gone to sleep, I still had to wait for the one minute spinup cycle. Even after playing the same album several times, I could hardly see the cache growing. I felt a bit disappointed.

I have no idea how the caching algorithm works, but I am starting to see a change. After a week I do not experience the lag anymore. Albums I play frequently start immediately. The cache hit rate over this week is over 80% which sounds good, no pun intended. The user interface of the NAS also feels snappier.

It is a bit surprising to see that the cache size is still only at 4.6GB. I play a lot of hires audio and I would expect a larger cache size. Let us see how this cache evolves with longer use.

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