On Mon, 2003-10-13 at 15:08, Hermann Himmelbauer wrote: > Hi, > I am considering buying a new Intel based Motherboard (875P chipset) with 2 > RAID-Controller on Board: ICH5R and Promise PDC20378. > > I want to know if the RAID1 functionality of Intel's 875P Southbridge (ICH5R) > is fully supported by Linux. I read that at the launch of the ICH5R only > RAID0 was supported but by a BIOS update, RAID1 is now also available. Is the > driver (if there is any) pre-alpha or has it somehow proved to be stable? > > Moreover I want to know if there are drivers for the Promise PDC20378. > > But here's another question: Let's assume those 2 RAID chips are perfectly > supported by Linux and you would want to set up a fast RAID1 solution with > e.g. 2* WD-Raptor SATA disks. There are 3 ways to do this: > > 1) Software RAID: Easy, no driver support needed, but would this be very CPU > intensive? Moreover is grub already capable to load the kernel from a RAID1 > device? Another disadvantage would be that during write operations the > traffic between the CPU and the disk subsystem is doubled compared to a > HW-RAID solution. > > 2) HW RAID with ICH5R: This variant has the advantage that the SATA-channels > are directly connected to the Chipset and do not stress the PCI-bus. > > 3) HW RAID with Promise > > Theoretically the read speed of a RAID1 device should be double of a single > disk. Anyway it seems that currently available HW-RAID1 solutions are even > slower than a single disk. What would this be like with Linux SW-RAID? Would > SW-RAID double the read-speed? > > What would you prefer? > > Moreover I would like to know which filesystem would suit best. For the > HW-RAID solutions this should not make any difference but I heard that e.g. > ReiserFS + Linux SW-RAID is quite slow. > I use ext3 + raid1 with two western digital 8MB cache disks. I get about 65mb/sec sustained read performance. With one disk, I get about 40mb/sec sustained read performance. The linux raid code read balances across disks, but doesn't write balance. The performance of the ataraid code is worse. I think it doesn't read balance, but I'm not sure. I do know that you probably want to stick with linux raid, or a real hardware raid controller that doesn't rely on drivers to concatenate/mirror the devices. Thanks -steve > Best Regards, > Hermann - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
