Sorry, I've looked at this again.

It's plausible that md's read balancing would increase the read speed,
but it appears that this is not the case. Are you using LVM? And the
readahead for the block devices are set appropriately? Distro? Version
of mdadm?

cc

On Fri, Oct 16, 2009 at 10:32 AM, adfas asd [off-list ref] wrote:

I was hoping to get better performance with RAID10 than from the raw disks, but that's turned out to not be the case.  Experimenting with the readahead buffer I get these bandwidths with the following command:
# time dd if={somelarge}.iso of=/dev/null bs={readahead size}

/dev/sd?
 1024 71.3 MB/s
 2048 71.2 MB/s
 4096 77.7 MB/s
 8192 69.4 MB/s
 16384 76.6 MB/s

/dev/md2
 1024  67.1
 2048  69.1
 4096  75.7
 8192  64.9
 16384 69.0

Using RAID10offset2 on 2 WD 2TB drives, and always the same input file.

Why would RAID10 performance be -poorer-?
If it weren't for mirroring, this wouldn't be worth it.






--
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

-- 
Chris Chen [off-list ref]
"The fact that yours is better than anyone else's
is not a guarantee that it's any good."
-- Seen on a wall
--
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