On Tue, Jun 2, 2009 at 12:59 PM, Gordon Messmer yinyang@eburg.com wrote:
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.
I'd advise anybody who manages server equipment always UPS it. It's not just power losses that can ruin your day, a power spike can take out a power supply just as easily and a UPS conditions the power so the output level is constant.
-Ross