Adding SSDs for Caching

[cmcigas]

I am building a new server for myself, I already added some vdevs a few weeks ago but I wanted to add some nvme ssds that I picked up for read and write caching. I noticed that when I go to add them to the pool, I also have to add a data vdev. Is this normal?

I do have two disks just sitting waiting to be added to the pool also so maybe that is why I am running into this issue? I dont have any data on the pool yet so I can just rebuild it but is there a way around this? Can I just force it?

 

[cmcigas]

Figured out my issue was due to having the log vdev on stripe, once I changed it to mirror I was fine to do this.

 

[NugentS]

Do you need a LOG drive - it is not a write cache
Do you need a L2ARC (Cache) Drive - it does not work the way you probably think it does. Also its 1.8TB - so you better have a shitload of ARC (memory) to run it.

 

[sfatula]

I would bother with l2arc unless your arc hit rate is not very good. You could actually reduce performance, it's more of a waste for most people. More memory far better than any l2arc.