Bill Davidsen wrote:

quoted

    16k read    64k write
  chunk
  size    RAID 5    RAID 6    RAID 5    RAID 6
  128k    492    497    268    270
  256k    615    530    288    270
  512k    625    607    230    174
  1024k   650    620    170    75
  

What is your stripe cache size?

I didn't fiddle with the default when I did these tests.

Now (with 256k chunk size) I had

# cat stripe_cache_size
256

but increasing that to 1024 didn't show a noticeable improvement for 
reading.  Still around 550MB/s.

Kind regards,

Thiemo