Re: Adding Reed-Solomon Personality to MD, need help/advice

["H. Peter Anvin" <hpa@zytor.com>]

Jeff Breidenbach wrote:
>>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.
> 

Well, most of them are implemented via tables (GF log table, etc.)  They 
tend to perform poorly on modern hardware.

	-hpa