On Fri, Feb 01, 2002 at 10:27:15PM -0200, Dinamica Sonora wrote: > If i understood well, only DPT can do hardware RAID, all other are "more > or less" software RAID. The ataraid support is just a layer between the > requests and the physical disks. yep > > I mean "more" when running soft RAID, without RAID controler, since all > disk requests/management would be done by kernel using main CPU and "less" > when running w/ a RAID controler since some of the disk requests would be > handled by the controler itself (releasing the CPU). OK. but what about an > onboard RAID controler? Wouldn't the performance be similar for both > controler RAID and soft RAID? In fact, no. Softwareraid will be faster. The kernel has more higher level knowledge and uses that to work more efficiently.... > So, why are there so many MOBO w/ RAID onboard? Looks nice on the box > How would one (performance) benefit from using a RAID 0 controler onboard > in a Linux system? For Raid 0 or Raid 1, software raid in practice always beats the pants of hardware raid, and doesn't use lots of cpu (think "100 cycles per 4Kb block"). Raid5 is a different story where the XOR operation takes cpu time; hower a pIV cpu runs at 2.2 Ghz while a raid controller cpu at, typically, 230Mhz.... Greetings, Arjan van de Ven
