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Re: [K12OSN] Linux "Software RAID"



Rob Owens wrote:

raid5: automatically using best checksumming function: pIII_sse
   pIII_sse  :  2604.000 MB/sec
raid5: using function: pIII_sse (2604.000 MB/sec)

I don't see any of that info on my systems with software RAID 1.

Raid1 doesn't do any calculations - it just tells the hardware to write twice and reads from whichever copy is faster. Any performance hit comes from CPU involvement during writes (not much unless you are on old IDE or USB connections) or overloading the PCI bus.

> What
do those values mean?  Are they read speads?  Write speeds?

That's the math to compute the parity that needs to be written along with the data. And if you have a failed drive in the set it will do a similar computation to reconstruct the data in degraded mode (where raid1 just reads the other copy at full speed).

--
  Les Mikesell
   lesmikesell gmail com


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