On Fri, Oct 16, 2009 at 10:32:14AM -0700, adfas asd 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.
try with layout=far - it is good for reading big files, maybe a factor 2
faster than layout=offset.
More on performance:
http://linux-raid.osdl.org/index.php/Performance
Best regards
keld
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