Nick Bryant nick@everywhereinternet.com wrote:
Indeed. I freaked out when I couldn't get my sata promise raid controlling working in Acer Altos series servers... Till I read an article that said in 2.4 its actually just as quick (if not quicker, depending on server hardware) to let the kernel deal with the raid stuff.
The Logical Disk/Volume Management (LDM/LVM) of the OS is always going to order, schedule and commit far more efficiently than a FRAID driver (FRAID cards have *0* intelligence, only a "trick" 16-bit BIOS that is _useless_ once the OS boots).
Software RAID-0 may be faster than hardware (especially if spread over cards on separate PCI channels).
Software RAID-1 and 10 require the I/O commit 2x the data over hardware RAID, which just takes the 1:1 stream.
Software RAID-3/4/5 push _all_ data through the CPU-memory- I/O interconnect, and is detrimental on the limited CPU- memory-I/O interconnect (the XORs aren't the problem), whereas hardware RAID-3/4/5 just takes the 1:1 stream.