Hello all! 

I have vSAN stretch cluster 12 nodes. Have one disk group per node (All flash).
1 x 1.46 TB Cache
4 x 3.49 TB Data

What is the best practice for expanding. I was thinking one more Cache disk and two more data disks so it would be:
2 disk goups per node:
1 x 1.46 TB Cache
3 x 3.49 TB Data
+
1 x 1.46 TB Cache
3 x 3.49 TB Data

1. These disks are expensive, could just have 1 more Cache and one Data in the same disk group, so it would be:
2 x 1.46 TB Cache
5 x 3.49 TB Data

Please advice