Re: dd performance test differences

[Adam Weremczuk <adamw@matrixscience.com>]

Hi Mike,

Thanks for the suggestion.

New test results with suggested parameters below:

Slower server
W: 13107200000 bytes (13 GB, 12 GiB) copied, 97.5106 s, 134 MB/s
R: 13107200000 bytes (13 GB, 12 GiB) copied, 28.6353 s, 458 MB/s

Faster server
W: 13107200000 bytes (13 GB) copied, 83.7368 s, 157 MB/s
R: 13107200000 bytes (13 GB) copied, 11.6786 s, 1.1 GB/s

No huge discrepancy but still something making me scratch my head :-)

BTW, small values can be useful when e.g. BBU fails and you want to get 
an idea about performance quickly:

dd if=/dev/zero of=test.bin bs=512 count=1024 oflag=sync
524288 bytes (524 kB, 512 KiB) copied, 25.101 s, 20.9 kB/s

---
Adam


On 02/11/18 12:40, Michael Stone wrote:
> That's a uselessly small block size & count. Try again with something 
> more like bs=128k count=100000
>
> Note that your dd test is a write test and your testparm is a read 
> test. It would probably be useful to also do a dd read test with 
> parameters above. (if=test.bin of=/dev/null)
>
> Mike Stone