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 you only use your RAID-10 array for a single "dd if=bigfile
of=/dev/null" then yes, it does not give you much over mirroring.
If you start using your drives for two "dd if=bigfile[12] of=/dev/null"
at the same time, you will notice the difference.
--
Tomasz Chmielewski
http://wpkg.org
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