I have a twelve drive md raid6 and am a bit puzzled about the raw performance I'm getting out of it.
Each drive can sustain about 200 MiB/s at the beginning of the drive so I expected something around 2.4 GiB/s read speed and 2GiB/s write speed when writing full stripes at the beginning of the raid array.
Unfortunately ... I am nowhere near those values when performing a stripe aligned dd write :
>> root@test:~# dd if=/dev/zero of=/dev/md1 status=progress bs=2560k oflag=direct
>> 12200181760 bytes (12 GB, 11 GiB) copied, 126 s, 96.8 MB/s
>> 4656+0 records in
>> 4656+0 records out
>> 12205424640 bytes (12 GB, 11 GiB) copied, 126.078 s, 96.8 MB/s