MSA2012FC - mixing SAS & SATA performance issues ?

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We are planning a VMWare ESX implementation, based around an MSA2012FC SAN. Ideally 6 x 300GB 15K disks in RAID 1+0 for up to 8 servers including Exchange & SQL. We do need some storage, a couple of TB will do and so we thought 750GB SATA drives in RAID-5. Will doing this impact on performance of the 15K SAS storage? I know we can mix SAS & SATA but there's nothing regards performance implications on any HP website I can find.