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?
Dan
Slavery was abolished in the 1800's.
b-
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