External storage questions

[hondaman]

I have a server and would like to attach both an external sata raid storage box, and a scsi raid storage box, home built. I kind of dont understand how it works. If I shut the power off on the server, and the power is still on on the external storage boxes, is that ok? What if the power gets shut off on the storage boxes but the server is still on? Will any of this corrupt the arrays? The OS is linux of course.