If you create a parity volume (RAID 5) and use a benchmarking program like IOMETER to test it, the throughput shows only 45 to 50 MegaBytes per second. A parity volume needs to be initialized. Wait until the initialization process has been completed by selecting the volume and then the task tab. You will then see bar showing the percentage of the task completed. Wait until it has finished and shows 100% complete.