Re: dmraid - where is the raid done?

["Brian J. Murrell" <brian@interlinx.bc.ca>]

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On Mon, 2008-10-27 at 20:12 -0500, Roger Heflin wrote:
> 
> If it is an out-of-kernel driver, then the work is being done in the 
> manufacturer's driver.

I see.

> If it is dmraid it is being done in the dmraid driver.

Ahhh.  So in the above "out of kernel driver" instance that is a case
where dmraid is not handling it, yes?

> If there is no underlying hardware to run the raid on then everything has
> to be done in the OS.

Indeed.  I had just wondered if these "fakeraid" solutions where at
least fanning out the copy (in the case of mirror) themselves, saving
the doubling of PCI bus traffic.

> All of the real raid cards have at least a
> really basic microprocesser on the card that takes care of things.

Yeah, I'm fairly familiar with the concepts of real RAID hardware.  It
was this new fakeraid I was wondering about.

Thanx for the enlightenment though.  The one last value that I had hope
for in the fakeraid arena seems to be invalid so I have to start to
agree with the documentation I've read and really have to wonder the
value of the fakeraid, especially and until the on-disk formats are
standardized.  Not being able to move fakeraid disks from one
manufacturer to another is a real impediment in my mind.

b.


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