Hello together!
I've a system with 8 SSDs (each ~500MByte/s read/write) connected to a LSI 9271-8i RAID-controller as a RAID0 array.
Under Windows I get write and read rates of about 4GByte/s.
Under Linux I test for example with
time dd if=/dev/zero of=/dev/sdX bs=1M count=8000
but then I only get this:
8000+0 records in
8000+0 records out
8388608000 bytes (8.4 GB) copied, 7.61166 s, 1.1 GB/s
real 0m7.613s
user 0m0.000s
sys 0m7.572s
So the rate is too low and the reason seems to be the CPU utilization because
dd is running on one core and its "system utilization" is at 100% during the whole runtime.
If I run 12
dd in parallel and write to the same device then the aggregated rates are ~3GByte/s.
The utilization of the benchmark
bonnie++ is also ~100%.
Hence I've these questions:
- Is there a way to get rid of this CPU-limitation during reads/writes?
I mean: The system has 2 processors with each 6 cores. So if dd uses write() or a similar call, is there no "paralelized version" under linux?
- Is there a benchmark which generates multiple threads/processes for concurrent reads/writes?
Many thanks for any help!