The Storage Manager does not work properly for RAID, so disregard what you are seeing. The command line is probably better. There is also quite a lot of information in the HowTo's.

BTW, you only need an SSD for a squid cache if you have a fast line, perhaps > 50 Mb/s, and, even then, if you have a fast line, you might as well turn the squid cache off. Personally I'd have installed onto SSD then put things like flexshares onto RAID (and perhaps backup /etc there as well).