[K12OSN] Linux "Software RAID"

[Rob Owens]

Dan Young wrote:
> On Fri, Aug 8, 2008 at 4:37 AM, Rob Owens <rob.owens at biochemfluidics.com> wrote:
>> I realize the ease-of-use advantage of hardware RAID, but I really was
>> talking about the performance hit only.
>>
>> Realistically, a hardware RAID costs about $300, and that could buy me a 2nd
>> 4-core processor.  I have to believe that a modern 4-core processor is way
>> more capable of handling a RAID rebuild than whatever chip is onboard a
>> hardware RAID controller.  Of course, I haven't done any testing...
> 
> If you have a md on Linux running somewhere, try "dmesg | grep raid".
> You'll see that the kernel tests several checksum algorithms, some
> using SIMD ISA extensions:
> 
> raid5: automatically using best checksumming function: pIII_sse
>    pIII_sse  :  2604.000 MB/sec
> raid5: using function: pIII_sse (2604.000 MB/sec)
> raid6: int32x1    312 MB/s
> raid6: int32x2    375 MB/s
> raid6: int32x4    351 MB/s
> raid6: int32x8    339 MB/s
> raid6: mmxx1     1023 MB/s
> raid6: mmxx2     1238 MB/s
> raid6: sse1x1     921 MB/s
> raid6: sse1x2    1261 MB/s
> raid6: using algorithm sse1x2 (1261 MB/s)
> 
I don't see any of that info on my systems with software RAID 1.  What 
do those values mean?  Are they read speads?  Write speeds?

Thanks in advance for educating me.

-Rob
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