From: Mickael Maddison mike@kamloopsbc.com
Hello CentOS, Does anyone know if there's a driver out there that'll enable CentOS 4.x to use the Intel Matrix SATA RAID settings on the 915 chipsets?
All FRAID cards do is setup the RAID organization in the 16-bit Int13h disk services. In other words, the vendor introduces its own data organization for RAID, instead of relying on the OS.
So there's really no such thing as a RAID driver for any FRAID card (Fake/ Free RAID) implementation. It's all software RAID. The system directly drives the ATA channels, which means the OS uses the standard ATA driver.
That means that the FRAID card must either:
A) Provide the FRAID logic as a kernel module
A few do, and it's a massive binary object that is kernel build-specific. The FRAID logic is licensed from a 3rd party, and that 3rd party makes all of its money from that proprietary logic, so it will never be GPL.
B) Write a data organization/interface wrapper kernel module to Linux's ataraid.c FRAID logic module.
The GPL/reverse engineered hptraid.c, pdcraid.c and silraid.c modules are examples that don't work well at all, and only for a few models of each.
C) Write a data organziation/interface wrapper to Linux's LVM/MD instead of the ataraid.c logic module.
This is far more ideal and higher performing, but it makes it OS-specific. I believe this might be what the RAIDCore cards do for Linux support.
Intelligent, hardware RAID don't have to do A-C, because the RAID logic is on-board in the firmware, driven directly by an on-board microcontroller or ASIC. FRAID cards use your host CPU and software.
That's why RAID are so cheap and have *0* additional hardware over a standard ATA controller.
-- Bryan J. Smith mailto:b.j.smith@ieee.org