Re: Software vs Hardware RAID 10?

[Goswin von Brederlow <brederlo@informatik.uni-tuebingen.de>]

Gabor Gombas <gombasg@sztaki.hu> writes:

> On Thu, Aug 30, 2007 at 10:03:34AM +0200, Goswin von Brederlow wrote:
>
>> You can test this with for example:
>> 
>> dd if=/dev/md0 of=/dev/zero bs=1M count=1024 &
>> dd if=/dev/md0 of=/dev/zero bs=1M count=1024 skip=1024
>
> The machine at my office (kernel is vanilla 2.6.22.1, i386):
>
> # (dd if=/dev/md1 of=/dev/zero bs=1M count=4096 iflag=direct &); dd if=/dev/md1 of=/dev/zero bs=1M count=4096 skip=1024 iflag=direct
> 4096+0 records in
> 4096+0 records out
> 4294967296 bytes (4.3 GB) copied, 81.1718 seconds, 52.9 MB/s
> 4096+0 records in
> 4096+0 records out
> 4294967296 bytes (4.3 GB) copied, 142.024 seconds, 30.2 MB/s

Just updated my kernel and I can reproduce your results:

# dd if=/dev/md1 of=/dev/zero bs=1M count=1024 iflag=direct
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 23.5635 seconds, 45.6 MB/s

# dd if=/dev/md1 of=/dev/zero bs=1M count=1024 iflag=direct &
  dd if=/dev/md1 of=/dev/zero bs=1M count=1024 skip=1024 iflag=direct
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 23.7129 seconds, 45.3 MB/s
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB) copied, 23.8732 seconds, 45.0 MB/s

So the problem seems fixed.

MfG
        Goswin