[CentOS] Supersize io operations (IO block size more than 4KiB) is split in to number of 4KiB blocks

Mon May 8 18:40:28 UTC 2017
Son Son <skmuttlu at gmail.com>

Concern: Supersize io operations  (IO block size more than 4KiB) is split
in to number of 4KiB blocks

Supersize io operations  (IO block size more than 4KiB) is split in to
number of 4KiB blocks

OS: CentOS 7.3

kernel Version: 3.10.0-514.el7.x86_64


Any IO (write) block size more than 4KiB is split in to number of 4KiB
blocks on Centos 7.3 ( where I don't see similar issue on 7.2). I have a
setup that involves TWO CentOS 7.3 servers. I tried to run 4MB IO on FC
LUN(s) on these servers discovered through Emulex LPe 16000 HBAs.

Changed ‘options lpfc lpfc_sg_seg_cn =>1024’ and ‘max_secors_kb =>4MB’
params towards attaining supersize IO ( 4MB block size) , however there are
no improvements in getting more than 4K block size IO.  There was no impact
from these changes.

Looking for a help to tune the system to attain supersize IO operation (4MB
writes)

Regards,

Sk