4 x 7200 RPM disk with ZFS in RAID 10
2 x Intel SSD with the following partition setup:
- mdadm running RAID 1 for installing CentOS 7 on a 20 GB partition (one per drive)
- One partition per SSD for ZIL/SLOG (5 GB mirror)
- One partition per SSD for L2ARC (rest of the drive, striped)
I'm running KVM on top of this setup with a ZFS ZVOL for each VM. It appears to the VM to be a normal block device and gains all the benefits of ZFS with compression, caching, data integrity, snapshots, and flexibility with the potential to do send/receive to another server to back up the entire VM at once.
The last point is something I haven't fully tested yet - my expectation is that a ZFS snapshot has the potential to catch the database in the middle of a transaction and cause a table crash or similar if you revert to the snapshot.