Anders Karlsson trudheim at
Mon Jan 2 09:56:06 UTC 2006

On 1/2/06, Mike Bird <mgb-ubuntu at> wrote:
> I'd be interested in seeing your statistics comparing reliability
> of hardware versus software RAID.  We run about fifty MDs here.
> Never had a serious problem due to the MD software,  although the
> infinite retries on resync errors can be annoying.

Reliability can be on par, -ish, if you are willing to spend the money
on the hardware, but then if you do buy the proper servers why be a
cheapskate and try and drop the price by a percent or two by dropping
hardware raid? Usually, people cutting cost using software raid has
also cut cost buying cheaper hardware (in the sense that it is not
enterprise calibre hardware). Hence they will have more failures on

I run MD at home, due to me having lost data because of a failing disk
in the past. MD is cheap and reliable enough for me. But if I was
running a business, I would use MD for only as long as it'd take to
get the funds together for proper kit. Like a FAStT 600 or similar. I
know that FCAL is expensive, but having spent years working with it, I
know it is reliable, and if SSA had been available for Linux, I would
have been happy using that.

MD does have a drawback, and that is that it takes CPU (sometimes
serious amounts of CPU) to do its raid. Perhaps if you dedicate
servers to do nothing but MD raid and serve those arrays to the other
machines via AFS or CODA...

Anders Karlsson <trudheim at>

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