i have 2 hdd and 1 nvme ssd
Possible? Sure. Create partitions and give those to ZFS. Be warned that SLOG and L2ARC do not do or help with what most people think they do. They are intended for special workloads that most don’t have to deal with. It may do nothing for you other than needlessly burn through your SSD write endurance.
Do you have sync writes? Then an SLOG may help. While consumer NVME drives are certainly way better than HDD’s, getting a device means for low latency small iops (optane) is better.
Have you examined your ARC hit rate and have a repeated random read workload that’s too big for ram, but will fit on an SSD. Then an L2ARC may help.
the thing is i need as much ram as i can for virtualization and adding L2 arc will help in my workload (muti user editing same large doc at same time)
i want to get a slog since i regularly have brownout druing rainy season
so what command i should use to do that zpool or fdisk i am on ubuntu server btw
If you’re doing this for a business then you will basically guarantee catastrophic data loss as the NVMe drive will be the critical point of failure.
I cannot recommend enough against doing this.
Please see this for the administration commands.
RAM is cheap. Just buy more.
Oh yeah it can definitely help with that, although you’ll see way more gains by just adding more RAM. If you’ve already maxed out your config then investing in a L2ARC will be the next recommended path.