ASM IO distribution on a SAN

The Oracle docs state that ASM can perform striping and mirroring. If I use ASM on a SAN how is it able to stripe? All it will see are mount points? My understanding is that it is possible create LUN(logical Units) and map them to individual disks or sets of disks and then possibly map those to mount points. Would this make it easier for ASM to handle IO distribution?

The project I am working will fully deploy with 5 billion inserts(all bulk loads using external tables) and have 4 million OLTP type queries/day (average query returns over 100 rows, but they are all index scans and the queries are not that complex). No updates or deletes.

I am trying to find ways to optimize our physical IO. We are using RAC so if I need more CPU we can add nodes.

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