Re: Harware vs Kernel RAID (was Re: External SATA enclosures: SiI3124 and CentOS 5?)

[Gordon Messmer <yinyang@xxxxxxxxx>]

On 06/01/2009 07:52 PM, Michael A. Peters wrote:
>
> I've read a lot of different reports that suggest at this point in time,
> kernel software raid is in most cases better than controller raid.

There are certainly a lot of people who feel that way.  It depends on 
what your priorities are.  Hardware RAID has the advantage of offloading 
some calculations from the CPU, and has a write cache which can decrease 
memory use.  However, both of those are relatively expensive, and 
there's no clear evidence that your money is better put into the RAID 
card than into faster CPU and more memory.  Another important 
consideration is that hardware RAID will (must!) have a battery backup 
so that any scheduled writes can be completed later in the case of power 
loss.  If you decide to use software RAID, I would strongly advise you 
to use a UPS, and to make sure your system monitors it and shuts down in 
the event of power loss.
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