How to maximize Optane for ZFS in ESXi


New Member
May 27, 2018
I’m planning a new build and consolidating the hardware I have for a new ZFS server. I currently have 1x M.2 905P Optane 380GB and 1x U.2 905P Optane 960GB that I bought separately when I found good deals. However, due to their mismatched sizing and I’m new to ZFS, I’m wondering if anyone with experience can offer help on how to maximize the benefits of my Optane SSDs.

My specs are the following:
CPU: dual Xeon 8176 ES
Memory: 384GB for ESXi 6.7u3 host and 256-280GB allocated for Solarish ZFS VM
Storage: 6-10 mirrored pairs of SATA HDDs allocated for ZFS pool
Network: 10GBE to all my servers

ZFS Use case: Mainly to offer a faster storage solution compared to UnRAID. I’ll be keeping UnRaid for media and backups, but ZFS will be the solution for iSCSI targets for ESXi. In it, I’ll be storing around 3-6 VMs (Windows, Linux), storing databases such as Nextcloud, Plex & Lightroom, and Veeam LTO8 tape cache.

I’m interested in using the Optane drives mostly for SLOG and special vdevs, and perhaps L2ARC if needed. Is it possible to organize the Optane drives by creating VMware datastores and offering them as separate partitions like this:
SLOG: mirrored 40GB + 40GB from each Optane drive
special vdev (metadata + small blocks + dedupe): mirrored 340GB + 340GB from each Optane drive
L2ARC: 580GB from U.2 drive if needed

I know that using the same disk for different tasks will impose a penalty. And ideally, I should have dedicated drives for each vdev type, but I’m wondering if this can be viable. Many thanks in advance!