Feizhou spake the following on 7/18/2007 11:58 PM:
Alvin Chang wrote:
On 18/07/07, Tony Mountifield tony@softins.clara.co.uk wrote:
In article f7iufv$1cc$1@softins.clara.co.uk, Tony Mountifield tony@softins.clara.co.uk wrote:
My question is: which kind of configuration will generally give me
better
performance? To use the IHC7 RAID-1 as currently set up, or to use
Linux
software RAID-1 as I am used to doing? Any other reasons to choose one over the other?
Thanks for the responses, confirming what I thought: disable SATA RAID and use Linux software RAID for mirroring. So that's what I've done.
It appears that my Centos 4.4 install didn't know about dmraid devices anyway.
I personally would give fakeraid a because the hardware chipset wouldn't take as much CPU time as soft-raid. Why are you using 4.4 instead of 4.5 as you mentioned in your previous post?
There is a reason it is called FAKEraid. They provide zero cpu offloading, they do not come with a chip that does raid processing let alone a battery backed up write cache. The chipset only handles SATA or ATA channels.
Oh, if you want to try the hardware raid is faster than software raid line, then I have got news for you. Some time back, there was this i960 chip from Intel that was very popular on hardware raid solutions. It sucked. It sucked big time. Yes, it did offload a fair bit of cpu processing from the AMD/Intel cpus then but the i960 was so slow, using software raid was just a no brainer since you get twice the speed for a 10% cpu load.
Today, hardware raid come with big memory caches and that is the only reason they are faster than software raid in certain cases like raid5. Any hardware raid card that does not come with a memory cache is not likely to be much faster than a software raid solution especially when using the more complicated raid arrays like raid5/6. You will notice that products from 3ware and Areca all now come with memory caches. There is no such thing as a cheap hardware raid card.
The i960 doesn't count, since it hasn't been used for a while. I think it was designed as a printer rendering engine processor, and was never designed for the load that raid imposed.