Re: Benchmarks: Linux Kernel RAID vs a Hardware RAID setup

[Bill Davidsen <davidsen@tmr.com>]

Keld Jørn Simonsen wrote:
> On Tue, Jul 15, 2008 at 10:40:26PM +0400, Brad Campbell wrote:
>   
>> Keld Jørn Simonsen wrote:
>>
>>     
>>> I would also welcome test with mobo HW RAID - Many mobo's today come
>>> with some HW raid functionality, and many people would be in the
>>> situation of whether to choose a HW or SW configuration.
>>>       
>> Do you have some pointers for information on motherboards that come with 
>> hardware raid? I'd be interested to have a look at them. I've certainly 
>> seen plenty of "fakeraid" systems, but I've not yet come across hardware 
>> raid on an MB.
>>     
>
> It is possible that I am thinking of what you call fakeraid.
>   

I like "firmware raid" better, but the bottom line here is that the raid 
is still done in the system CPU. These often have little or no hardware 
support, such as cache so that multiple drives can be written without 
passing the data through the system bus more than once (and chancing 
change while that happens).
> Anyway this is what many users buy and look at employing.
> And my understanding is that you can set up the mobo controller in the
> bios, and then have it running with Linux, without further software. 
>   

Yes, although the reliability of firmware raid under device failure 
conditions is dependent on the vendor, firmware level, etc, etc.
> I would then like to see what the differences are, and I hope to
> document that Linux raid is better... Anyway I am first and foremost
> just curious, and if HW/fake raid is faster or better, the I would
> gladly recommend it.
>   

Don't confuse HW and firmware raid, they don't have the same failure 
points and capabilities.

-- 
Bill Davidsen <davidsen@tmr.com>
  "Woe unto the statesman who makes war without a reason that will still
  be valid when the war is over..." Otto von Bismark 



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