disk-setup.sh

#!/bin/bash

# DANGER: ALL DATA WILL BE DELETED
# assumes disk order is consistent
# atobey@datastax.com 2015-05-09

export PATH=/bin:/sbin:/usr/sbin:/usr/bin:/usr/local/bin:/usr/local/sbin

die () { echo "FATAL: $*"; exit 1; }

set -x

# wipe all existing partitions
for l in c d e f g h i j k l m n
do
        for part in /dev/sd$l[0-9]
        do
                umount $part 2>/dev/null
        done

        sgdisk -Z /dev/sd$l
        dd if=/dev/zero of=/dev/sd$l bs=1M count=50
        sgdisk -og /dev/sd$l
done

# create a single large partition on each device
count=0
for l in c d e f g h i j k l m n
do
        count=$((count+1))
        sgdisk -n 1:0:0 -t 1:8300 -c 1:"Data drive $count" /dev/sd$l
done

# create two RAID0 volumes, each with half of the available drives
mdadm --create /dev/md0 --chunk=256 --metadata=1.2 --raid-devices=6 --level=0 /dev/sd[cdefgh]1
mdadm --create /dev/md1 --chunk=256 --metadata=1.2 --raid-devices=6 --level=0 /dev/sd[ijklmn]1

mdadm --examine --scan > /etc/mdadm.conf

mkfs.xfs -b size=4096 -d su=262144 -d sw=6 /dev/md0
mkfs.xfs -b size=4096 -d su=262144 -d sw=6 /dev/md1

I see that in script you are setting blocksize for xfs (-b) although in your guide your recommendations are for seting sector size (-s) to 4096.