SSD-cache on DS918+

[oRBIT]

When I'm creating a NVMe cache on my DS918+, DSM allows me to select the size of the cache. What's the purpose for this since I obviously can't use the space I'm not allocating as cache for anything else?

 

[jeyare]

more you can read in official Syno KB, there is a description
and here

 

[oRBIT]

Can't find any info about custom cache-sizes and why I am able to pick a smaller size than the NVMe since I can't use any space that I decide not for use with the cache.

 

[akahan]

It's because there's a tradeoff. Every 1GB you add to the SSD cache utilizes 416KB of system memory to address it. So if your demands on system memory are high, or you have insufficient system memory, you might choose to use less then the entire SSD cache available to you. System memory usage would be particularly high if you are running multiple VMs, for example. You definitely wouldn't be helping yourself if your SSD allocation caused you to hit the ceiling on system memory.