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Please don't make assumptions about what you think I meant.
There is absolutely, positively nothing about RAID 5 that is superior to RAID 0+1 or RAID 10 unless cost is your primary issue. The resiliency of a RAID 5 set would be no better (and in fact would be worse than RAID 10) and the performance can't possibly approach RAID 0, RAID 1, RAID 0+1 or RAID 10.
As for RAID 0+1 vs RAID 10, the only thing superior about RAID 10 is an extra degree of resiliency. However with the proper controller and driver a RAID 0+1 can enhance performance even further by permitting simultaneous reads and writes. In that case - the difference between logically mirroring a stripe and striping a mirror, there's a small tradeoff between performance and that extra degree of resiliency.
You may indeed be correct however, as I don't know for sure that the 3Ware supports that sort of multithreaded access. For $300, perhaps not...
I didn't assume anything about what you meant. I based my response on exactly what you wrote. You suggested RAID 0+1 for both speed and redundancy, and without having to spend an arm and a leg on a controller. And I disagree with that recommendation -- those requirements are met with greater resiliency using RAID 10.
RAID 0+1 offers no performance advantage over RAID 10. Neither needs beefier controller requirements than the other. And RAID 10 is more resilient in the various failure modes. The advantage is RAID 10 for that specific scenario.
RAID 5's advantage over both is a more efficient use of the available raw hard drive space. Both RAID 0+1 and RAID 10 lose half the hard drive space, which is a significant loss of money if using Raptors. Less hard drives = less heat, less power, and less chance of individual hard drive failure. RAID 5's read speed using a good controller is comparable to n-1 drives in a RAID 0, faster than RAID 1, and only slightly slower than RAID 0+1 or 10. Write speed, of course is where you may take the performance hit, and this is dependent on the controller. The 3Ware 9650SE can sustain over 100MB/sec RAID 5 writes. Resiliency of the RAID5 array is good, equal to the resiliancy of RAID 0+1, but RAID 10 can handle some multiple hard drive failure modes that RAID 5 can't. Of course, the 3Ware 9650SE card can now do RAID 6 which can handle 2 hard drive failures, at only a 20% write speed penalty over RAID 5.
The benefit/trade-off of RAID 5 is that you have to spend more money on the controller, but potentially less money on hard drives for the same space, speed, and safety. I like RAID 5's simplicity of setup, and the reduced drive count over RAID 0+1 & 10 translates into a heat & power advantage.
I will say that IOPs (I/O's per second) on RAID 0+1/10 probably perform much better than a typical RAID 5 implementation. This translates into better performance for high-transaction applications like databases. However, for System6's audio applications, it would be dubious if this is an advantage. In fact, with audio applications (working with large files like .wavs), transfer rate would be a better benchmark of his expected performance gain than anything else.
Perhaps Seagate 7200.10 drives (perpendicular recording, 7200 RPM) in a RAID 0, RAID 10, RAID 5, or RAID 6 are a good solution for his system. Depends on how much redundancy he wants and how much money he wants to spend on a controller.