L2ARC tuning guide and common misconceptions

[jro]

@etorix

But, on second thought, maybe we’d need an extra parameter box to account for write cache/networking speed. Base recommendations are for 1 GbE; switching to 10 GbE takes up to two txg worth of RAM space for the write cache, reducing available ARC size by a not-unsubstantial amount, and then it seems that “L2ARC footprint at 10/25% RAM” does not fully capture what’s going on…

It’s doing percent of total RAM, not percent of ARC. If you want to try to figure out ARC size, the javascript is here: https://jro.io/l2arc/l2arc.js