> The fundamental problem is that generic RS requires table lookups even > in the common case, whereas RAID-6 uses shortcuts to substantially > speed up the computation in the common case. If one wanted to support a typical 8-bit RS code (which supports a max of 256 drives, including ECC drives) it is already way too big to use a table. RS is typically done with finite field math calculations which are - relatively - fast but they are much heavier than a parity calculation. Here is one commercial benchmark, note the throughput numbers at the bottom of the page. http://www.4i2i.com/reed_solomon_codes.htm I can easily imagine CPU being the bottleneck for a large RS RAID, especially when run in degraded mode. Rakhi Motwani and I worked on a RS based, RAID-like storage system, although not for magnetic disks. Search for "Collocated DataGlyph Protocol" if you are interested. It was a lot of fun. Cheers, Jeff - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
