A client is looking at moving from Oracle 10g on AIX5.3, all JFS2 file systems to ASM. The SAN is HDS: USP-V fronting USP and AMS arrays. HDS supports Thin provisioning with Oracle ASM based storage so it would be nice to have for migrations,they wont need to have all of the storage up front and according to Oracle its OK http://www.oracle.com/technology/products/database/asm/pdf/hds%20hdp_bestpractice_wp%203-14-2008.pdf Page 22 is a little worrying based on Oracle's testing, there is a potential of 8-25% adverse performance impact when thin provisioning is used. I guess thats when ASM is striping AND HDS is striping in the background too - ASM must be told external RAID is being used basically.
As long as they do as recommended, ie all RAID Groups and Parity Groups in a pool are taken from multiple/different back end adapters, same disk size/speed, same RAID levels they should hit the performance statistics mentioned under "ASM on HDP - Recommended configuration".
RAID Groups and Parity Groups are just terminology for the group of disks configured in a RAID set in HDS Modular(AMS) & Enterprise(USP) arrays respectively.