After using Intel’s ICH10R for a long while, I was always baffled by the poor real-life performance of my RAID drives. I mean if I benchmark them, they were OK, but when I needed them while CPU was busy with something else - like video encoding - the performance wasn’t there. I mean a RAID 5 with three discs would crawl to 18-20MBps transfer rate with no reason… except the CPU load being 100%.
Decided to buy a dedicated RAID controller. At first I tried an Adaptec one, but it conflicted with the Intel one in my system (Dell T3500). Plus it was requiring active cooling, like in a server enclosure.
Then I got from ebay this 3Ware AMCC 9650SE-4LPML RAID controller. I saw in reviews that it had a PowerPC PPC405CR cpu at 266MHz, 256MB of DDR2 cache. Put it in the PC, no conflicts with Intel ICH, loaded drivers and updated the firmware to the latest.
Well… I am looking at 83-90MBps transfer rate, while the main CPU is under heavy load. It is amazing what a dedicated CPU can do for RAID. So, at this point, no more software (Intel) RAID for me.
PS: I just bought a battery for this RAID controller too.
RAID5 is well known for being a lot CPU-intensive. All the calculations are done at the CPU. You should consider a higher-end cpu.
I forgot to say, I have a 6 core, 12 thread Xeon CPU running at 2.67GHz.
I am using this 3ware raid controller for raid 10 on four wd blue 1tb hard drives. The serial write and read are 300mb/s. It is mainly for storage so I am very happy with it.
Btw is intel raid software raid?..
Yes, is driven by main CPU.
Not really, because you can/have to configure it from within the BIOS. Furthermore it requires an appropriate on-board hardware device (Intel RAID Controller).
For details you may look >here<.
I found a good discussion here. It is not pure software RAID but no doubt it uses some CPU. But it also does some on its own so “it reduces the CPU load”. Like plutomaniac said, RAID5 uses more CPU in this case.
Back to RAID-5, looks like it is rarely used nowdays. I think you should serious consider using RAID10 instead. I had one drive failed once and swapped it. There is no down time. Even if two out of four drive fails, if lucky, it is still recoverable (with some special software).
Based on the same concept, the CPU is “hardware” because it is configured from BIOS (you have to load specific code for specific CPU’s) 
Now, the BIOS has a mechanism that allows extensions. Those are pieces of software that are run on the main CPU to allow access to new ports and I/O devices, not present in original PC design, at boot time.
This is what Intel RAID is, nothing more. There is no special block to calculate the parity, but just a piece of software (actually two - one in BIOS and one in drivers) running on main CPU.
@Fernando
Do you recommend that I create a raid array? Should I have gotten 2 x Samsung 850 EVO 250GB in RAID 0 instead? From your benchmarks it seems like RAID 0 does benefit SSD. I thought it doesn’t. Also, given my plans to get more storage with mechanical drive(s), should I run two 1TB WD Black in RAID 0 or just get one 2TB WD black and keep everything at AHCI?
@hoeman :
Since your questions have nothing to do with the topic "Modded Intel AHCI and RAID Drivers", I have moved your recent post into an already existing thread named "RAID Performance", hoping, that this is ok for you.
My answer depends on
a) what you are mainly doing with your PC (Office tasks/Internet surfing/Gaming/Video encoding etc.) and
b) your financial situation.
My answer is "Yes", if you are working very often with very big sized files (e.g. Video encoding) and have enough money to buy a second SSD.
It really does, but you will not recognize any performance boost while doing standard tasks (writing a letter or an eMail, surfing in the internet etc.). Most important for the "normal" daily PC performance are the 4K scores. If you compare the 4K benchmark results of a single SSD running in AHCI and 2 similar SSDs as members of a RAID0 array, you will see, that there is no remarkable difference. So you only benefit from the better RAID0 performance while reading/writing much bigger sized files.
If you just need place to store your data, I would prefer the latter option.
Remember: If any member of a RAID0 array gets corrupted, you will automaticly loose all data from your complete RAID0 array. For me a RAID0 array only makes sense, when the OS is installed onto it. For storage purposes a RAID1 array would be the better, but less performant option.