On Tue, 2005-07-12 at 22:52 -0400, Dan Christensen wrote: > Ming Zhang <mingz@xxxxxxxxxxx> writes: > > > On Mon, 2005-07-11 at 11:11 -0400, Dan Christensen wrote: > >> I was wondering what I should expect in terms of streaming read > >> performance when using (software) RAID-5 with four SATA drives. I > >> thought I would get a noticeable improvement compared to reads from a > >> single device, but that's not the case. I tested this by using dd to > >> read 300MB directly from disk partitions /dev/sda7, etc, and also using > >> dd to read 300MB directly from the raid device (/dev/md2 in this case). > >> I get around 57MB/s from each of the disk partitions that make up the > >> raid device, and about 58MB/s from the raid device. On the other > >> hand, if I run parallel reads from the component partitions, I get > >> 25 to 30MB/s each, so the bus can clearly achieve more than 100MB/s. > >> > >> [...] > >> > >> System: > >> - Athlon 2500+ > >> - kernel 2.6.12.2 (also tried 2.6.11.11) > >> - four SATA drives (3 160G, 1 200G); Samsung Spinpoint > >> - SiI3114 controller (latency_timer=32 by default; tried 128 too) > > > > only 1 card? 4 port? try some other brand card and try to use several > > cards at the same time. i met some poor cards before. > > Yes, one 4-port controller. It's on the motherboard. > > I thought that since I get good throughput doing parallel reads from > the four drives (see above) that would eliminate the controller as the > bottleneck. Am I wrong? > have u try the parallel write? > Dan > - > To unsubscribe from this list: send the line "unsubscribe linux-raid" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
