Read cache support in Truenas scale

[noahnao]

I am confused it seems that Truenas scale does not support any cache other than ARC, but on Truenas's website, it states that the Truenas minis support read and write caches. Can someone explain?
Thank you.

 

[sretalla]

There's a bit of a complication around the terminology in use that some of us here would disagree a little with the marketing terms thrown around even in official documentation.

Write cache is RAM only... SLOG (often referred to incorrectly as write cache) isn't that, rather a separate drive to hold a copy of what's in RAM before a sync write is acknowledged as complete).

Read cache is possible both with ARC (in RAM) and L2ARC (on some disk that's hopefully faster than your pool or it makes no sense).

Both types of read cache can be turned on or off for individual datasets or pools and can also be set to only handle data or metadata.