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#21
RAID 5 with as many disks as you can support will give you the best performance. I have been using RAID for years and RAID 5 will do it if you have 5 or more disks. I have RAID 5 on a 12 disks server and the read/write is blazing fast. RAID 6 will use dual parity and will slow you down a bit because the system is having to write the parity data twice. This does allow for more disks to fail without total loss of data but in your case you are looking for speed. Having 6 disks in a RAID 5 array will give let you have up to 2 disks fail without losing the Array. You would still be working but in severely reduced read/write access. You would need to replace the disk/disks and let the array rebuild to get back to full speed.
Here is some information that might help (note it is mostly correct): RAID - Wikipedia, the free encyclopedia